Full Bust Adjustment Guide | Giant FBA on a Dartless Knit Bodice (aka: Adding a Dart When You Need One)

The deal with Giant full bust adjustments

Being pregnant, my boobs have grown 6 inches in the last 6 months — I’ve gone from a garment sewing DD or F cup to a garment sewing K cup. (Remember that bra cups aren’t the same as your garment sewing cup size! Learn more about determining your garment sewing cup size here!)

Even with the ~80 designers on the Busty Pattern Database who draft for larger cup sizes or offer cup options, only one offers a cup option that fits me — Porcelynne’s I/J cup in her tank series is just right.

So full bust adjustments and I have become best friends lately. And not just small, 2-3″ FBAs, but BIG HONKIN FBAs. Even on a DD garment cup size pattern — the largest cup size offered by a substantial number of designers — I need a 6″ full bust adjustment (3″ per side). On a B cup pattern — the size that most designers draft for — I need a 9″ FBA (4.5″ per side).

The trouble? No fitting book or FBA tutorial I’ve seen really gets into what it looks like when you’re adding this much.

Which is annoying because it looks different. It can look a lot different.

So I’m going to start showing you what my FBAs look like when I’m adding 6-9″ to my patterns.

Fitting the Perfect Maternity Tee

This particular FBA was inspired by my search for a perfect maternity tee — partially because I need a lot of new shirts right now, and partially because I’m planning a bodycon style dress for my baby shower, and I needed a base pattern.

I started with the Agnes Maternity Top from Tilly & the Buttons (which also has a non-maternity version), but this tutorial can easily be used for any number of dartless knit top patterns, such as the Cashmerette Concord, Itch to Stitch Glenelly, or the Laela Jeyne Indigo Bodysuit.

Do I have to add a dart?

Okay, I’m really sorry. But I have bad news. Yes, if the difference between your high and full bust is more than, say, 7″ (17.8 cm), you’re probably going to need to add a dart, even to a knit bodice — especially if you’re hoping for a fitted look.

If you’re okay with the bodice being a more loose fit at the waist, you might be able to get away with rotating the dart out and easing the side seam — a process we’re not going to get into today. But, if you want a fitted look, it will be simply impossible to ease your front and back side seams together after adding so much. (Trust me, I tried. A lot. It doesn’t work.)

That said, I really don’t think the dart is super noticeable, and I promise it’s less noticeable than the armpit wrinkles that result from ill-fitting knit tops. (Tell me if you think the dart is noticeable in this side view!)

Getting prepared for your FBA

Choosing a base size

We’ve talked about this before, but I want you to start with your high bust measurement, braless. (The reason we take this measurement braless is because you’re trying to capture as little breast tissue in it as possible, and bras push breast tissue up!)

If you’re working with a pattern that lists high bust measurements on its size chart, that’s great! The work is done for you! Choose your size based on the one that corresponds with your high bust measurement.

But, if your pattern is like the T&B Agnes, you’ll need to do a little math, which will require you to know what garment cup size the pattern is drafted for. In my case, I reached out to T&B and was told that their maternity patterns are drafted for a D garment cup — 4″ difference between high and full bust. So I knew I needed to add 4″ to my high bust measurement. (If you’re working with a usual pattern with a B cup draft, you’ll add 2″ to your high bust measurement.)

For me the math looked like this: 35″ + 4″ = 39″

This number should then correspond with the bust measurement on the pattern.

On the Maternity Agnes, this put me between a size 4 and 5. Because I wanted a more fitted look, I went with a size 4.

How do I know how much to add? Math time!

On a woven garment, this is easy. If the Maternity Agnes were woven, I’d simply take my full bust measurement minus the full bust measurement for which it is drafted, and that would tell me how much to add. Divide this by two, and you get how much you need to add per side.

For example:
My bust: 46″
– Drafted bust: 38″
= 8″
Divided by two (since there are two sides to a front bodice!) — 4″ per side

However, I don’t like to do things this way for knitted/stretch patterns. My reluctance comes from the fact that stretch percentages mean you’re really adding more. For example, if your fabric has a 50% stretch, adding 4″ total is really adding a maximum of 6″, while adding 8″ total is really adding a maximum of 12″ — that’s a 6″ difference in maximum stretch for what’s supposed to be a 4″ difference. This problem is exponential, so the larger your FBA the more skewed things can end up being by simply adding inches like you would with a woven.

So I like to look at percentages. Enter the finished garment measurements.

For the size 4 I’m making, the finished bust measurement is 36.5″. It’s drafted for a 38″ bust. I want to figure out what this is as a percentage, so I’ll take 36.5 divided by 38 to get 96% — meaning this is drafted for 4% negative ease.

Now, I need to figure out what 96% of my full bust is: 46″ times 96% (0.96) = 44.16″. I’m going to go ahead and round that down to 44 to give me a nice even number (and I can confidently do that because I know my knit stretches plenty to cover a .16″ reduction). This is what I need my finished bust measurement to be: 44″.

Next, I’ll need to figure out how many inches that has me adding, so I’ll subtract the pattern’s finished bust measurement from my own needed finished bust measurement: 44″ minus 36.5″ = 7.5″. This shows me I need a total of a 7.5″ FBA, so 3.25″ per side.

If reading this is confusing and you’d like to see a video version, I walked through this process on instagram live here!

Doing the FBA

Finding your apex

Now that you’ve done your math, you can get working with your pattern! Here’s what my pattern looked like before I made any changes:

You’ll notice there’s no apex marked on this pattern. No worries! We’re going to find our own apex.

Put on a top that’s made from a fabric with a similar stretch percentage. Using washi tape, mark where your bust is fullest — this is sometimes the nipple, but not always. Look for the “peak” of your “mountain.”

(My washi tape is really lightly colored! I apologize that it’s hard to see here!)

Now, take off this top and fold it at center front. Lay the folded top under the front bodice pattern, matching the shoulder seam and center front (being mindful that seam allowances mean your pattern should slightly overhang the shirt).

You can see my washi tape through the pattern paper. This is where I’m going to mark my apex.

Preparing the pattern

Now that we’ve marked the apex, we’re going to cut the pattern at the waistline. On the Agnes, the waistline (or, in this case since it’s a maternity pattern, the empire waist) happens to be at the lengthen/shorten line, but this may not always be the case. Cut the pattern at the narrowest part and put the bottom of the pattern aside. We’ll come back to it later. (If you’re working with a bodice pattern that ends at the waist, great! No need to cut at this step.)

Now, we need to make some markings. First, draw a vertical line, parallel with your grain line, from the bottom of your pattern to the apex. We’ll call this Line A.

Now, draw a second line from your apex to about 1/3 of the way down the armscye. We’ll call this Line B.

Some tutorials will tell you to put this mark lower on the armscye. While this works for those who need to add fewer inches, for larger FBAs, putting this line low on the armscye causes too much armscye distortion, so higher is better.

Important: At Line B, mark your seam allowance. This will be very important at a later step.

Third, you need to draw a line from your apex to the side seam. This is Line C.

You can really put this anywhere along your side seam that you’d like, but keep in mind that where you place it on the side seam will essentially end up being the top of your bust dart. I like to make mine slightly angle upward, but only slightly. If I wanted a fully horizontal dart, I’d need to make this perpendicular to my grain line.

Finally, mark a Line D perpendicular to Line A about an inch above your waistline.

Cutting the Lines

Now it’s time to start cutting! But, before we do, do yourself a favor and stick a piece of scotch tape on your apex and on the seam allowance mark at the armscye.

Okay, now, starting from the bottom of the bodice, cut upward through Line A to the apex, then from the apex through Line B — stopping at the seam allowance mark. From the opposite side, starting from the armscye, cut through Line B, again stopping at the seam allowance mark.

Your pattern should be hanging on by a thread of paper at the seam allowance mark, allowing you to pivot at this point.

Now, starting at the side seam, cut through Line C, cutting to but not through the apex — creating another pivot point where the paper is holding on by a thread.

Your pattern will look like this:

Adding inches

Now it’s time to add some inches! I like to tape down the center front side of my pattern (on this pattern, the right side of the picture) along Line A onto another piece of pattern paper. I then draw a line however many inches from Line A on the extra pattern paper:

This line gives me something to line up the side seam side of Line A with, which is the next step.

Pulling the side seam side (here, the left of the photo) down and out to match that side of Line A with the line you just drew.

Note: You’ll see I’m only adding 3.5″ here, though earlier I said I needed a 7.5″ FBA, so 3.75″ per side. Well, that was a mistake. But since the pattern uses fabric with at least 50% stretch, I decided to just rock a bit more negative ease and not worry about it.

Evaluating Armscye Distortion

So this is what my FBA would look like. If I was adding fewer inches, I’d tape it down and call this my new pattern, essentially. But I’m adding a lot of inches, so I need to evaluate something first: How much did my armscye get distorted?

Depending on the pattern, the armscye distortion might be minimal and totally okay! In this case, tape everything down and use this as your pattern!

But, as you can see here, I got a lot of armscye distortion. It’s basically a J pattern, and I know that’s going to be super uncomfortable. But there’s a solution!

Doing the Y FBA

We’re going to add one more line. Draw a line from the apex to the middle of the shoulder seam — usually there’s a notch here, and if so, use that! This will be Line E.

Just like with Line B, you need to mark the seam allowance on Line E.

Now, cut from the apex along Line E to but not through the seam allowance mark. Then cut from the top of the shoulder along Line E to but not through the seam allowance mark, creating a pivot point with a thread of paper at the seam allowance.

Again, spread down and out to match the side seam side of Line A with the marker you created earlier to show how many inches you’re adding.

At this point, you need to decide how much of the added inches you want coming from the armscye versus the shoulder/high bust area. In the above slides, you can see how you can manipulate where things lay to have more of the added inches be along Line B or along Line E.

This is all about knowing your body. Adding more to Line E — like in the second picture — prevents more armscye distortion, but adds more width at the high bust/chest. Adding more to Line B — like in the third picture — creates more armscye distortion, but doesn’t add as much at the high bust/chest. Or you can choose something like the first picture, with roughly equal amounts distributed between Line B and Line E.

I don’t like to have too much added at the upper bust for my body, so I lean toward adding more to Line B than Line E — adding just enough to line E to avoid significant armscye distortion. I went with something like the third picture.

Once you have everything where you want it, go ahead and tape everything down, just being sure not to tape along Line A below Line D.

Adjusting length

Now we need to bring the center front down to the level of the side bodice. Extend Line A on the center front side down to be even with your new waistline from the side seam side, and draw a horizontal guideline at the same level as your new waistline on the side seam side.

Now, cut along Line D, completely detaching that bottom piece. Tape this down along the guidelines you just created, like so:

This is what we have so far, and we’re pretty much there!

Finishing Touches

Smoothing the armscye

Now we need to smooth out the armscye. You can do this by eye (which is honestly what I usually do), or break out your French curve to do it *technically* correct.

At this point, I like to drop my armscye just *a tiny bit* — like 1/4 to 3/8″ — making sure the armscye remains the same total length by measuring where I’ve dropped it.

Drawing your new dart

You now need to draw your new dart. Start by measuring the opening of the triangle you’ve created, and marking the center point.

Now, draw a line from this center mark on the dart to the apex. You’ll see here I moved my apex a bit. This was an experiment, and I wouldn’t recommend it. Just use the apex you marked — since the dot has been divided, choose the one on the center front part of your pattern.

Now, mark a spot along this center dart line some inches from your apex. The number of inches depends on the size of your bust. Here’s what I’d recommend as a starting place:

I+ garment cup9″+ (22.85 cm+) full/high bust difference2.5″ (6.35 cm)
G-H garment cup7-8″ (17.8-20.3 cm) full/high bust difference2″ (5 cm)
DD/E-F garment cup5-6″ (12.7-15.2 cm) full/high bust difference1.5″ (3.8 cm)
D garment cup or smaller4″ or less (10.2 cm) full/high bust difference1″ (2.5 cm)

So I made my mark 2.5″ back from the apex. This will be my vanishing point, or where the dart will actually end. You usually don’t want the dart ending too close to your apex, because this will make your bust look verrrrry pointy. (If pointy is the look you’re going for, then make your vanishing point closer to your apex!)

Now, you’re just going to connect this vanishing point to your dart legs. This is your finished dart!

Note: Do you need to split your dart? I answer this question visually. My dart was about 6″ long and 3-5/8″ wide, and, looking at it, I thought it would sew up fine. If your dart looks really wide, you may want to split it into two darts. This post goes over the how-to on splitting darts.

Truing the Side seam

We now must true our side seam. To do this, fold your dart as if it was being sewn. I prefer to have my dart go upward rather than pressing it down, as most instructions indicate. I find this makes a smoother line for larger busts. (Thanks to Cashmerette for the tip several years ago!)

You can either fold your dart up or down. It’s up to you.

I like to tape this shut using washi tape, so it stays closed while I deal with my side seam, but using a tape that won’t rip the paper when I remove it.

Use your French curve or eyeball a slightly curved line, connecting the armscye to the lower side seam.

You’ll see that I had a big jump from the upper to lower side seam. Since you can always remove but can’t add, I chose to go with the outer side seam — so the placement of the lower side seam. It’s worth noting, however, that I ended up skimming about 3/8″ off this spot when I sewed my muslin, so I probably could have/should have gone with the smaller of the lines — where the side seam is on the upper part.

Truing your waist

As you may recall, you’ve added inches (in my case, 3.5″) to your bust level down — including your waist. Well, if the waist was the correct size on the original pattern and you want the bodice to be fitted at the waist, this isn’t going to work. We need to reduce the waist.

On a woven, this would be easier. I’d recommend taking a bit from the side seam and adding a waist dart or two.

But here, I didn’t want to add a waist dart. This is a tee shirt after all! So it’s going to have to all come from the side seam.

To do this, mark along the waistline 3.5″ (or however many inches you added in your FBA) inward from the side seam. Draw an S curve, starting at your bust height and ending at your waist marker, like this:

You can do this with a French curve or by eye. I started with my French curve and ended by eye, which is why my line is so ugly 😂

I also had a bit of an extra challenge because I was making this with an empire waist rather than a natural waist, so that gave me less space to gradually skim off the side seam than you’d have using a natural waist. If you’re using a natural waist, this line shouldn’t look quite so angular.

Now, to finish truing the dart, cut along this line:

Open your dart back up, and you’ll see your finished side seam!

Reconnecting with lower pattern

Now our last step is to reconnect our upper pattern with our lower pattern!

Essentially, you just need to match your lower pattern to your upper at the side seam and center front.

At this point, I also do a bit more truing of the side seam and cut it out:

You’re finished!

Yay! All done! Here’s my finished pattern piece:

Now cut and sew the pattern as usual. If you have an extreme angled side seam like me, it might be worth reinforcing the side seam at that point with some seam tape or elastic, just to add some strength since the force of the fabric is a bit wonky there.

I feel pretty awesome about this pattern! I can’t wait to sew up my baby shower dress 🙂

If you follow Sew Busty on instagram, you’ll know that I ended up needing to tweak the sleeve for my fuller biceps, but the bust was on point!

Full Bust Adjustment Guide | Gathered Bodice FBA

If you’ve followed me for a while, you probably know I LOVE a good jumpsuit. I know a lot of people are anti-jumpsuit because they have to get naked to go to the bathroom or whatever, but, to be completely honest, IDGAF. I love them. They’re ultimate comfort.

So, when I found out I was pregnant, I immediately knew I needed to make myself a maternity jumpsuit. Onto a pattern search!

I checked all my normal busty-friendly designers: Designer Stitch, Itch to Stitch, Cashmerette. None of them had a maternity jumpsuit (or really many maternity patterns at all! Cashmerette has a few, but they don’t yet come in her smaller size band, which is where my upper bust falls). I went through the Busty Pattern Database hoping for a good option, and, alas, didn’t find one.

So I got desperate and I went to etsy: “maternity jumpsuit pattern.” And I found this:

Butterick 6226. Maternity jumpsuit of my dreams.

I immediately ordered the pattern. The only problem? I’d have to do an FBA. And, not just a simple, darted FBA. A gathered bodice FBA.

Thank goodness I had done this before, because the results were amazing! I love this jumpsuit.

Gathered Bodice FBA Tutorial

Let’s get started, shall we?

choosing a base size

Just like with other full bust adjustments, the first step is to figure out what base size you’ll be making. Choose based on your high bust + 2″ as the “bust” measurement on the chart. I’ve talked about this before, but most FBA tutorials will have you choose based on your high bust substituted for the size chart’s “bust” measurement. I’m honestly not sure why tutorials teach this way, as this instruction fails to consider that almost all patterns are drafted such that the high bust is 2″ smaller than the full bust.

Thus, if the high bust measurement is not offered on a pattern, you must add 2″ to your high bust measurement, and choose the size with a bust measurement that most closely corresponds to this HB+2. My high bust measurement is about 35″, so I need a size with a bust measurement that is around 37″. According to the size chart on the Butterick 6226, that put me at a size 16.

Now, let’s take a quick moment to talk about Big 4 pattern sizing and why I ultimately chose a 14 even though the boob math put me in a 16: After reading reviews of this pattern and chatting with some folks on Instagram who had made this pattern before, the feedback was unanimous: This pattern runs big. That wasn’t a surprise; almost all Big 4 (Butterick, McCalls, Simplicity, and Vogue) run big. Most people I talked to said they got the best fit by choosing two sizes down from what they measured. Since 14 was the smallest size I had, though, I decided to go for it. (After making, I can confirm I probably could have made a 12, had I had the pattern for it.)

Okay, back to the FBA.

Doing some full bust adjustment math

Now, to start our FBA, we must do a little math. Butterick, like most pattern companies, drafts its patterns for a 2″ full bust to upper bust difference. My full bust is currently 45.5″, and my high bust is 35″ — meaning I have a 10.5″ difference. I need to subtract 2 from 10.5, for a total of 8.5. This means, in theory, I should have done a 8.5″ full bust adjustment, adding 4.25″ on each side. If you are working with a woven pattern, this is absolutely what you should do.

But this jumpsuit is a knit garment with a lot of ease, so I decided to do a few more steps.

First, I looked at the finished garment measurements. At a size 14, the finished bust measurement of 43.5″, so it’s drafted with an intended 7″ of positive ease (since the 14 is intended for busts of 36″). My chosen fabric also has 30% comfortable stretch (meaning not stretching it to it’s absolute limits), so—if I made the pattern as-is—I would have ended up with a possible 56.5″, after stretch.

As those of you who follow me on instagram know, I thought about being lazy and just making the pattern as-is. I asked you all. And you all very wisely told me to do the damn FBA.

But I didn’t necessarily want the full 7″ of positive ease, so I decided to do a smaller FBA than the basic [my full bust minus high bust] – 2″ equation was telling me. So I settled on doing a 5″ FBA—adding 2.5″ on each side. This would result in a finished, unstretched bust measurement of 48.5″—so 2″ of positive ease. This also meant that, if my boobs keep growing (please NO!), the garment could comfortably stretch to 63″.

Alright. Let’s do the thing. Add 2.5″ on each side.

Marking the pivot points

The apex was conveniently marked on the Butterick 6226!

(If, on your pattern, the apex is not marked, you’ll need to find its approximate location. The pattern may indicate bust-to-bust measurement, which can be divided in two and measured from the center front to find the horizontal alignment of the apex. Similarly, some patterns will list a shoulder point to bust measurement, which can then be measured from the shoulder point on the pattern to find where the apex lands vertically. Find where these points intersect, and you have your apex! If your pattern doesn’t list any of this, just make your best guess as to the apex location.)

You’re then going to draw two lines, seen in my photo in red: one vertically down from the apex to the waist, and one diagonally from the apex to the armpit, about 1/3 of the way up. We will call the vertical line “line A” and the diagonal line “line B.”

The next step is to draw two horizontal lines: What we’ll call “Line C” will go from the apex horizontally to the side seam. What we will call “Line D” will go horizontally from Line A to the center front. Don’t worry too much about exact placement of Line D — it’s really not important. Just needs to be somewhere from Line A to center front.

Cutting your pivot lines

Now, we’re going to begin snipping. Cut along Line A and Line B to the seam allowance. Snip carefully on Line B at the seam allowance to allow it to hinge—cutting to, but not through the seam allowance line.

adding Room for large breasts

Place your pattern on another sheet of paper, and tape down the right side of your hinge. Now, measure from the right side of Line A to however many inches you need to add — in my case, 2.5″. Draw a line on the scrap paper to mark this measurement. We’ll call this “Line E.”

Now you’re going to cut through Line C. Hinge the left side of Line A to meet Line E. Tape this down for now, but with the recognition that you’re going to have to close Line C in a few steps.

Truing the length

Next, you’re going to cut along Line D. I like to draw a straight line down from the right side of Line A so I know where I’m going to reconnect this cut off piece in the next step.

Tape down the piece you just cut off below Line D to your pattern, keeping it in line with the right side of Line A:

Then, we’re going to untape Line C. I know, taking tape off is a bitch, but I find it less fiddly than not taping down Line C in the earlier step. Up to you, I suppose.

You’re going to close Line C, creating a weird, contorted looking pattern piece. It’s all okay. I promise.

We’re nearly done! Your next step is to draw a curve to close off the bottom of your pattern piece. You can see my curved line in red, below. You can use a French curve to do this, but I honestly just freehanded.

Cut out your pattern, and voila! You have a newly-FBA’d pattern.

The only further change you’re going to have to make is that the gathering line — marked on my pattern piece as a purple dashed line — will need to follow the line of the bottom of your pattern piece, curve and all.

Dealing with the Waist

Usually, when we do large FBAs, we have to redraw the side seam or add a waist dart to prevent from adding room at the waist. But, with a gathered bodice, the extra room you added at the waist is going to be dealt with when you gather the waistline. You’re just going to have more gathers than someone with a smaller bust would.

Sewing the B6226 — General Thoughts

I’m glad y’all talked me out of being lazy and into doing a full bust adjustment! The jumpsuit feels like it fits well, with a bit of room to grow in the bust when my milk starts coming in.

The jumpsuit definitely feels a bit roomy through the shoulders, waist and hips, and I certainly could have sized down to a 12 if I had owned that size in the pattern. But it’s comfy even in the 14, so I’m not too worried about it.

There’s definitely plenty of room for my belly to grow. In fact, there’s so much room at the front crotch that things look a bit strange seated. This is really common in maternity wear, even store bought, so I’m not concerned. It just means my belly has plenty of room as it expands.

Have questions about this full bust adjustment tutorial for large busts? Drop a comment below or or ask on the Sew Busty Facebook group or subreddit.

Community Blog | Fitting Fancy Fronts: Full Bust Adjustment for Midriff + Princess Seam Top – Tia Dress and Peplum with Karey

Sew Busty has been doing an excellent introductory series on getting started on sewing for big busts, including introduction to doing Full Bust Adjustments (FBAs). While doing my two posts on doing an FBA on a wrap dress or top for Sew Busty, it occurred to me that because being able to do an FBA for various styles of garments is such an essential skill for busty sewers, it would be good for more experienced sewers who want to extend themselves, to do a series of posts on doing FBAs for less common or more challenging styles, for which standard FBAs won’t work.

Also, while Sew Busty has developed an extensive database of designers who provide patterns for a range of cup sizes, only a handful go up to my cup size. While of those that do have larger cup sizes, some only provide them for larger base sizes. In order to have a full choice of styles to sew, I had to develop skills in doing FBAs. Other members of the Sew Busty community are in the same boat, and learning to do a wider variety of FBAs will expand your sewing options.

Figure 1: Finished Tia peplum

This post includes the details of the tutorial for the FBA Laura Nash, Sew Chic Patterns, provided for the vintage inspired LN1312 Tia Dress (Figure 2a) in her Craftsy Class: Sew Vintage: The Flirty Day Dress. This dress has a princess seam bust section, and a separate midriff section attached to a skirt. To save fabric while testing the fit, I hacked the dress into a sleeveless peplum top – Figure 2b). I provide a simple skirt hack for drafting your own peplum below.

While this tutorial was developed specifically for the Tia dress, there are many dresses with similar bodices. The recently released TINAlisa jersey Vicky dress (Figure 2d) does not have the midriff section, but does have the princess seam bust section. This is one of the first designs TINAlisa has released with a large bust front, but the designer, Martina Blasius, also always includes an FBA instructions for the specific design (see Note* below), and all designs include seamlines that make large bust fitting easier.

Before I retired, I had planned to copy a Mix-It-Up hack by one of the Craftsy participants, which combined three of Sew Chic’s designs: the Tia bodice, the Beatrice sleeve and skirt, and the Phantom sleeve cuff (shown in Figure 2c)), but I don’t often have the need for such formal dresses anymore. Many other patterns have midriff panels, which may need to be adjusted if you do an FBA, and the Tia FBA instructions can also be used for any princess seam FBA. I think it is a much simpler adjustment than the one most tutorials provide.

Figure 2: Style examples of princess seam bust with midriff panel: a) Tia dress; b) Tia Midriff; c) Tia, Beatrice, & Phantom mix-up; e) TINAlisa Vicky

SewBusty has tutorials on the two main ways of determining the cup size you need, one is primarily used for sewing clothes, and the other used to be the main way to measure for bra cups, but some pattern companies mix it up, including Cashmerette.

While the Tia pattern doesn’t include cup sizes, the FBA tutorial specific to this style of bodice provides instructions for (sewing cup) A (cup reduction) to DD cup – calculated by subtracting high bust (HB) measurement from full bust (FB) measurement. Cashmerette, on the other hand. uses bra cup sizes.

Figure 3: My cup size(s)

Because the Craftsy class materials didn’t go up to my cup size, Laura of Sew Chic provided details for the adjustments I needed, and information for going up additional cup sizes. Unfortunately, that information was provided in the questions feature on a platform that got closed and sold on. So while the class is still available on the new platform, and the Sew Chic FBA tutorial is also available on their website, the information about doing a bigger FBA is only in my class notes, hence my wanting to share it here. Before making any adjustments to a pattern, follow the steps in Figures 4a) and b), and make changes to traced pattern, not original.

Figure 4: a) trace pattern pieces; and, b) mark every seam allowances (5/8″ for Tia) on each piece. I trace onto non-woven tracing Vilene, which is partly transparent, cheap, strong, flexible, and drapes like fabric, so is excellent for tissue fitting and adjusting the pattern..
*Note: all pattern adjustments are made from sewing lines not from cutting lines, hence the necessity to mark all the seam allowances (SA). It also allows for accurate pinning for tissue fitting.

Figure 5 shows the steps for making the FBA.
a) Mark a line through the bust apex at the point of greatest width on the pattern (a). You will need to adjust actual bust apex, and possibly find tune extension curve in tissue fit and muslin.
b) Spread the Side Front (SF), hinging at the side seam sewing line, and opening in a wedge at the bust apex, as per the amount specified in column 2 in Figure 6. Spread the Centre Front (CF) by the amount specified in column 4 in Figure 6. Note that as cup size increases, so does the amount the CF is spread increases by more than the SF increases per cup size.
c) Extend the curve of the apex on the SF by the amount specified in column 3 in Figure 6.

Figure 5: FBA illustrations

Figure 6 provides the amounts of spread and extending for SF and CF for a woven dress. The instructions for the FBA for the TINAlisa Vicky dress are almost identical, except amount of spread is for knit dress. See Note* below for details.

Figure 6: Bust adjustment guide: amount to spread and extend for each cup size
*Note: the amount the CF is spread/reduced is the same for the A cup, but for C to E the amount the CF is spread increases with each size. There is no B cup on the chart because the pattern was drafted for B cup.


Although the chart does not have any extension on the CF on the seam over the apex, I had to extend my CF apex seam by about the width of the seam allowance. This is just one of the things that tends not to extrapolate smoothly as you go beyond a DD cup. I have my suspicions that this is one of the reasons designers limit their cup sizes to DD because bigger than that creates distinct design and fitting issues. This is just one of the reasons for tissue fitting and making a muslin if you have to adjust for larger cup sizes, as we are getting in the realm of ‘honking great darts’.

Finally, you need to ‘walk’ the apex seamline of the SF along the apex seam of the CF. Threads Magazine has an excellent tutorial, if you don’t know how to do this, including a video. See ‘How to Walk the Seamline’. This ensures the princess seam on SF and CF match. If they are not the same size, adjust how much you spread the CF, then walk again to recheck and mark notches on both pieces.

Before I show you my fitting steps, I want to show you the scale test I did using my scale b-cup and FBA bodices, fitted over scale boobs. I found this test allowed me to distinguish the fitting adjustments that were specific to doing an FBA on this bodice, and additional adjustments due to specificity of my particular body proportions, separately from those due to my cup size.

Figure 7 shows how a facsimile of the Tia bodice (b) (namely princess seam and midriff section) can be obtained from a sloper transformation (a). c) juxtaposes my scale B-cup and FBA boobs, while d) shows the scale ‘Tia’ bodice looks folded over the scale boobs. This order reflects narrative convenience rather than construction order. I actually placed my unmarked B-cup and FBA slopers over the scale boobs in order to mark the UB and above bust seam locations, and then marked up and cut the seam lines.

Figure 7: drafting facsimile of Tia bodice from B-cup and FBA scale bodice slopers
a) bodice cup lines marked on B-cup sloper (left) & FBA sloper (right) b) Side & midriff darts closed, UB and princess seams opened & side darts transferred to them. c) scale B-cup boobs (left), FBA boobs (right) d) cut out B-cup & FBA bodice halves (from b) taped and placed over scale boobs in c).


What I discovered was that, apart from the FBA, adjustments I made to the pattern during tissue fit and muslin were not directly attributable to the FBA. Although some may be common for those needing an FBA. For example, I deliberately kept the apex of the large half scale boob at the same height, in order to minimise the number of variables I changed. But in terms of real boobs, while there are some high sitting large ones, they are more inclined to sit lower than smaller boobs, as gravity works its magic.

So although 7d) shows the height of the midriff the same for both B-cup and large boobs, that is more a product of the test set up design, than based on any reflection of reality.

Figure 8: tissue fit comparing size 8 B-cup bodice with adjusted bodice
a) size 8: back and waist too narrow; FBA bodice, with wide back adjustment & waist graded out
b) B-cup excess back length, UB seam too high on bust; FBA bodice, waist shortened

My tissue fit and muslin confirmed I needed to grade out at waist, do large back adjustment, shorten midriff, and lower bustline, as well as do FBA.

Whereas the midriff on the B-cup and large bust are the same height in 7d) of the half scale model, I had to drastically shorten the midriff as shown in the tissue fit in 8a).

Figure 9: a) fine tuning muslin; b) Front midriff, black size 8, blue adjusted midriff, graded out & shortened c)Tia size chart, with my sizes marked

While I traced size 8 and did an E cup FBA, I also needed to shorten the back and midriff, as I am 5’2”, rather than the 5’6” the Tia pattern is drafted for. My large bust and short stature meant the 1” to 1¼” neckline trim looked too large. A large FBA often means design lines and proportions on a garment no longer work, and need some adjustment. I trialled ¾” and ½” trim on the Sew Chic Facebook group, and I agreed with the consensus that the narrower trim looked better.

Figure 10: a) final dress; b) comparing ½” trim on left with ¾” trim on right

Bonus Peplum hack
Peplums are commonly drafted as a full or half circle, but my square hips don’t really suit either the circle skirt on this dress, or as a peplum. Instead I drafted my peplum from a straight skirt that fit. Folding out the darts and spreading along the hipline.

If you prefer a full peplum you can slash the skirt from hem to waistline and spread the hem more. If a peplum top comes with a more full skirt than you prefer, you can reverse the process, slash from ham to waist, and overlap at the hemline.

Figure 11 slash and spread peplum
a) straight skirt cut at peplum length b) darts folded out, and hem spread c) extra slashes opened out. Reverse to reduce peplum spread.

Note*: TINAlisa Vicky Pattern
TINAlisa patterns are in German and don’t have seam allowances included (common in European patterns), but don’t let that put you off. You can upload the instruction pdf file to this Free Online Translator site (screenshot shown in Figure 12a), which will translate the text to English (or whatever language you prefer) while preserving format and images (Figure 12b). For the large busted, it is easier to do an FBA without seam allowances, as they have to be removed from patterns that include them before you do the FBA anyway.

Figure 12: a) screenshot of document upload box (you may need to scroll down to find it);
b) sample translated document: Vicky FBA instructions

My next blogpost will feature a TINAlisa FBA for a more complex bodice.

Karey Harrison is a feminist philosopher of science and linguistics, environmentalist, retired academic, home baker, sewist, gardener. Karey also wrote the guest blogpost: #AllButtsWelcome: Unmentionables: Crotch Variation in Pantie Fitting. You can catch Karey on instagram @kareylea and see Karey’s academic profile here.

FBA Guide + Amelie Dress Sew Along Week B | Full Bust Adjustment on Non-Traditional Darts (Double Underarm Dart Version)

For August and September at Sew Busty, we’re doing a button challenge! Post a make that features buttons on instagram with #sewbustychallenge by September 30 for a chance to win a prize!

As part of that challenge, we’re doing a sew along for the Untitled Thoughts Amelie Dress – a cute little number that features buttons down the back of the skirt, as well as an open (but bra-friendly!) back. (Check out the picture of the dress on today’s post, as I accidentally earlier shared a picture of the non-bra friendly! For the full sew along, including bonus content, click here!

This week, I’m pleased to welcome Brittani of Untitled Thoughts back to the blog to talk us through doing a full-bust adjustment on the Amelie! Without further ado, here’s Brittani:

Hello Sew Busty Community! Brittani here from Untitled Thoughts. I am so excited to be writing up this guest blog post for the Sew Busty blog, especially seeing as I have been meaning to whip up a tutorial on this very subject: Performing an FBA on the Amelie!

Performing a Full Bust Adjustment (FBA) on a garment can already feel intimidating. Throw a Center Front waist dart into the mix and it can feel downright paralyzing! 

Have no fear! Adjusting your Center Front Darted pattern to fit your unique and beautiful shape is relatively simple and utilizes many of the same techniques as working on a normal FBA.This post will be fully dedicated to the act of making your alterations on a Center Front Dart specific pattern, in this case, the Amelie Dress. 

Let’s Get Started!

You will want to begin this process by first tracing off your front bodice pattern along with any important markings on your pattern such as:

  • Grainline
  • Darts
  • Apex Point
  • Notches
  • Lengthen/Shorten Lines
  • Size + View

I will be dividing this tutorial up into two groups: Single Dart and  Double Dart. Depending on what size you are making of the Amelie + which Cup option you have chosen, you will notice that there is either a single under arm dart or a double underarm dart. Each of these needs to be worked on slightly differently, which is why I have divided this tutorial into two parts! If you’re looking for the double underarm dart version, click here!

Double Dart FBA

To start, you will draw the following lines on your front bodice pattern piece:

  1. Directly through the center of your Center Front Dart to your Apex
  2. Perpendicularly from the Apex down through the Waist
  3. From your apex to your armhole (You will want to draw your line roughly ⅓ of the way from the under arm seam to prevent distortion in the armscye)
  4. From your Apex horizontally through the Center Front
  5. Directly through the center of your Upper Underarm Dart to your Apex
  6. Directly through the center of your Lower Underarm Dart to your Apex

Now that all your lines are in place, let’s get to cutting and hinging our pattern out! There are a few places we will be cutting. It’s important NOT to cut through our entire pattern piece. We want to leave a smidgen of the pattern intact so that we can hinge the pieces around and not accidentally distort the outer pattern edges too much!

The first set of lines you will want to cut through are lines 1 + 3. 

I forgot to mention, we need to mark out our seam allowance right at our armscye where line 3 passes through. This is the point where we will stop cutting to create a hinge!

To create a little hinge in your pattern (which allows you to shift your pattern open), snip from your armscye to — not through — the seam allowance mark you just made.

Next, cut line 2, starting from the center of your dart and ending right at the apex point. Be sure you don’t cut your piece completely off – you need to leave the tiniest bit of paper so that you are able to hinge your pattern, rather than having it come apart in puzzle-like pieces.  

Finally, cut through Line 5 + 6 ending right at the Apex. 

See how I am able to lightly pull my pattern piece and it opens up, yet all the pieces are still intact? This is what we are going for! Don’t worry if you accidentally cut through your pieces (as I have done many times!) Simply tape your pieces back together at the “hinge” point, and try cutting it again. It gets easier with practice!

For this next part, you will need some tape, scrap paper, a pen, and the measurement you plan to increase your pattern piece by. I am going to be doing an imaginary FBA of ½” (1,3 cm) for my sample. 

With your supplies in hand (and possibly a large cup of tea at the ready!), it’s time to adjust!

Gently pull the bottom edge of your pattern pieces until they start to spread apart. I like to place my ruler right at my apex point so that when I am sliding my pattern out, I can stop as soon as it reaches the measurement I am aiming for. In this case, ½”  (1,3 cm).

You may have noticed that I didn’t open up my CF dart and instead hinged it near the apex. The reason for this is because when performing an FBA, it is common to wind up with a new dart that becomes too wide compared to its length. When a dart is too wide for its respective length, this drastic change can cause the bust points to be rather… pointy. For some, this is a non-issue, but for many, avoiding a point at the end of our darts is paramount. This is actually why there are two underarm darts in this pattern – they were added to help redistribute the excess fabric after my testers informed me that the bust points were just too pointy. 

But what is the right width to length ratio for your dart?

Honestly, the answer to this question depends. It depends on your cup size, the location of the dart, the fabric you are using, and your own personal preferences. I wish that I had a sure fire answer that would work 100% for everyone, but I don’t. (If you know of a general guideline, feel free to share! A quick internet search yields next to nothing regarding the proper ratio to maintain.)

For myself, I go based on gut instinct for the most part. I’ve made a fair share of garments with darts that were too wide (as was the case with the Amelie at first!) and wound up with a dart point that was quite pointy. As my own personal rule, I try to keep all my bust darts less than 4” (10 cm) wide by 6” (15 cm) long.   

When in doubt about your bust width to length ratio, the easiest solution is to simply transfer the excess width of your dart into a second dart which you can easily do with the under arm darts if you’d like. 

All of that to say, I didn’t widen the CF dart because I know that it is already around 4” (10 cm) wide by 6” (15 cm) long and I don’t want to push those limits further. 

But now there is some excess right at the waist seam that we don’t want there. It’s time to transfer it! To start, make sure that you have taped the bottom of line 1 shut so that it doesn’t try to move on you. Then, gently close line 2 and tape it shut as well. 

Now all that excess from line 1 + 2 has been transferred into your underarm darts – yay! This is where the fun begins! You can now play around with altering your darts to see what works best for you. You can try eliminating a dart or even transferring one of those darts to a new location – the possibilities are endless!

For this tutorial, I am going to stick with simply dispersing the excess evenly between the two darts. 

Place a piece of scrap paper under your altered underarm darts and go ahead and tape everything you currently see in front of you down to prevent anything from shifting out of place!

I know that was a LOT of work! You are nearly there, but now would probably be a great time to take a mini break. Feel free to stretch, take a quick walk around your neighborhood, or drink a cool glass of water! When you come back, we will finish this tutorial by truing up your pattern!

Feeling refreshed? Then let’s dive back in and finish this alteration up!

Usually, it is at this point that you would typically be cutting through line 4 and shifting that piece down to match your altered bodice. However, since we have relocated all of the added space normally added to the CF dart into the existing under arm darts, you won’t need to adjust that pattern piece. 

To start, you need to draw out your new underarm darts. To do this, first mark your new Apex point. It will be exactly ½ way between where you split your apex in half. 

Now, measure out a point approximately  2” (5,1 cm) from your apex point along the centerline of your underarm darts. These are your new dart points. 

Next, connect your new dart point to the dart legs i.e. where you slashed and spread your paper on your side seam.

Repeat these same steps with your CF dart, but this time, mark 1” (2,5 cm) from your apex point before connecting your dart legs. 

Finally, one-by-one, close your darts temporarily. Cut off the excess paper under your side seam and then open your darts back up. 

Hooray! You now have a fully completed Center Front Dart bodice with an FBA perfectly suited to your body! It was a long process but I hope that you found it enjoyable and are excited to have a pattern that more closely fits you!

FBA Guide + Amelie Sew Along Week B | Full Bust Adjustment on Non-Traditional Darts (Single Underarm Dart Version)

For August and September at Sew Busty, we’re doing a button challenge! Post a make that features buttons on instagram with #sewbustychallenge by September 30 for a chance to win a prize!

As part of that challenge, we’re doing a sew along for the Untitled Thoughts Amelie Dress – a cute little number that features buttons down the back of the skirt, as well as an open (but bra-friendly!) back. (Check out the picture of the dress on today’s post, as I accidentally earlier shared a picture of the non-bra friendly! For the full sew along, including bonus content, click here!

This week, I’m pleased to welcome Brittani of Untitled Thoughts back to the blog to talk us through doing a full-bust adjustment on the Amelie! Without further ado, here’s Brittani:

Hello Sew Busty Community! Brittani here from Untitled Thoughts. I am so excited to be writing up this guest blog post for the Sew Busty blog, especially seeing as I have been meaning to whip up a tutorial on this very subject: Performing an FBA on the Amelie!

Performing a Full Bust Adjustment (FBA) on a garment can already feel intimidating. Throw a Center Front waist dart into the mix and it can feel downright paralyzing! 

Have no fear! Adjusting your Center Front Darted pattern to fit your unique and beautiful shape is relatively simple and utilizes many of the same techniques as working on a normal FBA.This post will be fully dedicated to the act of making your alterations on a Center Front Dart specific pattern, in this case, the Amelie Dress. 

Let’s Get Started!

You will want to begin this process by first tracing off your front bodice pattern along with any important markings on your pattern such as:

  • Grainline
  • Darts
  • Apex Point
  • Notches
  • Lengthen/Shorten Lines
  • Size + View

I will be dividing this tutorial up into two groups: Single Dart and  Double Dart. Depending on what size you are making of the Amelie + which Cup option you have chosen, you will notice that there is either a single under arm dart or a double underarm dart. Each of these needs to be worked on slightly differently, which is why I have divided this tutorial into two parts! If you’re looking for the double underarm dart version, click here!

Single Dart FBA

To start, you will draw the following lines on your front bodice pattern piece:

  1. Directly through the center of your Center Front Dart to your Apex
  2. Directly through the center of your Under Arm Dart to your Apex
  3. From your apex to your armhole (You will want to draw your line roughly ⅓ of the way from the under arm seam to prevent distortion in the armsyce)
  4. From your Apex horizontally through the Center Front

I know that generally when you are doing an FBA on a bodice pattern, you have a line that is drawn from the Apex perpendicularly down through the waist seam. For this particular bodice, though, I found that the line was too close to the CF dart, plus the same outcome is possible by working with only the CF waist dart. So that’s what we will be doing here!

Now that all your lines are in place, let’s get to cutting and hinging our pattern out! There are a few places we will be cutting. It’s important NOT to cut through our entire pattern piece. We want to leave a smidgen of the pattern intact so that we can hinge the pieces around and not accidentally distort the outer pattern edges too much!

The first set of lines you will want to cut through are lines 1 + 3. 

I forgot to mention, we need to mark out our seam allowance right at our armscye where line 3 passes through. This is the point where we will stop cutting to create a hinge!

To create a little hinge in your pattern (which allows you to shift your pattern open), snip from your armscye to — not through — the seam allowance mark you just made.

Next, cut line 2, starting from the center of your dart and ending right at the apex point. Be sure you don’t cut your piece completely off – you need to leave the tiniest bit of paper so that you are able to hinge your pattern, rather than having it come apart in puzzle-like pieces.  

See how I am able to lightly pull my pattern piece and it opens up, yet all the pieces are still intact? This is what we are going for! Don’t worry if you accidentally cut through your pieces (as I have done many times!) Simply tape your pieces back together at the “hinge” point, and try cutting it again. It gets easier with practice!

For this next part, you will need some tape, scrap paper, a pen, and the measurement you plan to increase your pattern piece by. I am going to be doing an imaginary FBA of ½” (1,3 cm) for my sample. 

With your supplies in hand (and possibly a large cup of tea at the ready!), it’s time to adjust!

Gently pull the bottom edge of your pattern pieces until they start to spread apart. I like to place my ruler right at my apex point so that when I am sliding my pattern out, I can stop as soon as it reaches the measurement I am aiming for. In this case, ½”  (1,3 cm).

Slide a scrap piece of paper under your pattern and tape the apex side of your garment to your scrap piece of paper to help keep it from sliding all over the place. Don’t tape the dart side down just yet as we might need to take a look at some things first!

When performing an FBA, it is common to wind up with a new dart that becomes too wide compared to its length. When a dart is too wide for its respective length, this drastic change can cause the bust points to be rather… pointy. For some, this is a non-issue, but for many, avoiding a point at the end of our darts is paramount. This is actually why the certain sizes of the Amelie DD-Cup option has two additional side darts! They were added to help redistribute the excess fabric after my testers informed me that the bust points were just too pointy. 

But what is the right width to length ratio for your dart?

Honestly, the answer to this question depends. It depends on your cup size, the location of the dart, the fabric you are using, and your own personal preferences. I wish that I had a sure fire answer that would work 100% for everyone, but I don’t. (If you know of a general guideline, feel free to share! A quick internet search yields next to nothing regarding the proper ratio to maintain.)

For myself, I go based on gut instinct for the most part. I’ve made a fair share of garments with darts that were too wide (as was the case with the Amelie at first!) and wound up with a dart point that was quite pointy. As my own personal rule, I try to keep all my bust darts less than 4” (10 cm) wide by 6” (15 cm) long.   

When in doubt about your bust width to length ratio, the easiest solution is to simply transfer the excess width of your dart into a second dart which you can easily do with the under arm dart if you so choose. For my particular FBA, it looks like the CF dart is exactly  4” (10 cm) wide by 6” (15 cm) long, so I won’t need to adjust the underarm dart at all!

I also went ahead and checked my under arm dart width and length and they both looked good to me! If anything, I bet I could get away with making the dart a bit shorter in length. 

Once your two darts are looking good to you, tape them down to the scrap paper underneath and give yourself a high five!

I know that was a LOT of work! You are nearly there, but now would probably be a great time to take a mini break. Feel free to stretch, take a quick walk around your neighborhood, or drink a cool glass of water! When you come back, we will finish this tutorial by making some final adjustments and truing up your pattern!

Feeling refreshed? Then let’s dive back in and finish this alteration up!

The final step before truing your pattern is to shift the right bottom bit of your bodice down so that your waist lines line up again. This will also give ample room for your garment bodice to fall over your bust without riding up in the waist area.

To do this, cut completely through line 4.

Then shift your pattern piece down until the waist line is about even. Make sure that you keep your grainline in the same place as you move your pattern piece down (you want it to remain a straight line). Tape your pattern piece in place. 

Now come the finishing touches! To start, you need to draw out your new underarm dart. To do this, first mark your new Apex point. It will be exactly ½ way between where you split your apex in half. 

Now, measure out a point approximately 1” (2,5 cm) from your apex point along the centerline of your CF dart. This is your new dart point. 

Next, connect your new dart point to the dart legs i.e. where you slashed and spread your paper on your side seam.

Repeat these same steps with your underarm dart, but this time, mark 2” (5,1 cm) from your apex point before connecting your dart legs. 

Finally, one-by-one, close your darts temporarily. Cut off the excess paper under your side seam and then open your darts back up. 

Hooray! You now have a fully completed Center Front Dart bodice with an FBA perfectly suited to your body! It was a long process but I hope that you found it enjoyable and are excited to have a pattern that more closely fits you!

Full Bust Adjustment Guide | Sleeveless Princess Seam FBA

For Community Thursday this week, I’m doing something a little different and joining in the fun of a community sewing challenge! When Jess (@SoWhatIfISew) asked me to participate in her #SewNewInJune challenge, I KNEW this meant I needed to expand my horizons. I love sticking to my comfort zones: cotton poplin, patterns with built-in cup sizes, minimal pattern adjustments …

As you probably know I’m a pretty lazy sewist. I’m more here for the creative parts of sewing, like choosing which fabric to use with which pattern, than the technical parts. I suck at spatial reasoning, geometry, and math, and therefore I’m not the biggest fan of pattern adjustments.

But I knew #SewNewInJune meant I should do an full bust adjustment. I haven’t done an FBA in … probably a year. But here I am, running a blog called Sew Busty and being challenged by Jess to try new things.

So I chose an FBA that I’ve personally seen people struggle with: the sleeveless princess seamed full bust adjustment. And Sew Over It was kind enough to gift me the Rosie dress pattern to work my magic! (While Sew Over It is drafted for a D cup at larger sizes and offers cup options at all sizes in some of their patterns, the Rosie dress is drafted for a B cup at my size.)

While doing research for this, I discovered a couple of things:

One: It’s different enough from a traditional princess seam FBA that this alteration can be intimidating.

On a traditional princess seam full bust adjustment, you use the armscye as an anchor point, like in this tutorial from the Curvy Sewing Collective. But, on a sleeveless dress with princess seams, you don’t have a traditional armscye, but are instead altering part of the neckline, so it can feel a bit tricky. It’s honestly not that much different in practice, but it definitely feels different.

Two: Most full bust adjustment tutorials assume a small (1″ or so) full bust adjustment.

My bust certainly isn’t the biggest, but I need a 3.5″ total full bust adjustment, or 1.75″ on each side. This is much bigger than the 1/2″ on each side that most tutorials expect you to be doing. For example, I tried to follow this tutorial from Closet Core Patterns that was written for a dress with very similar lines to the Rosie, but unfortunately, it wasn’t cooperating with my large bust.

Sleeveless Princess Seam FBA Tutorial

Alright, LET’S GO!

choosing a base size

The first step is to figure out what base size you’ll be making. Choose based on your high bust + 2″ as the “bust” measurement on the chart. I’ve talked about this before, but most FBA tutorials will have you choose based on your high bust substituted for the size chart’s “bust” measurement. I’m honestly not sure why tutorials teach this way, as this instruction fails to consider that most patterns are drafted such that the high bust is 2″ smaller than the full bust.

Thus, if the high bust measurement is not offered on a pattern, you must add 2″ to your high bust measurement, and choose the size with a bust measurement that most closely corresponds to this HB+2. My high bust measurement is somewhere between 34.5 and 35 depending on the time of day/month, so I need a size with a bust measurement that is somewhere between 36.5 and 37″. On the Rosie, the size 12 has a 37″ bust, so I selected this base size. As a bonus, the size 12 also has a 30″ waist, which is very close to my 29.5″ waist.

The only place I didn’t match the size 12 (aside from my full bust, which we will get to …) is the hips, where I’m around a 37.5″. The size 12 accounts for a 40″ hip. BUT I decided not to grade the pattern down at the hip because the Rosie is designed to have a free-flowing skirt: The finished garment at size 12 has 86″ of fabric at the hips, meaning there’s 46″ of ease built in … what’s a few more inches of ease at that point?

Doing some full bust adjustment math

Now, to start our FBA, we must do a little math. As I mentioned, the Rosie is drafted for a 2″ full bust to upper bust difference. I have a 5.5″ difference. So I need to subtract 2 from 5.5, for a total of 3.5. Then, because you’re really working on half of your bodice, you need to divide this by 2. For me, 3.5/2=1.75, meaning I need to add 1.75″ on my bodice pattern.

Marking the apex and pivot points

Because the apex is not marked on the Rosie, you need to find it. On a princess seam, the apex is somewhat easy to find: It’s the place where the curve is largest. I marked this point on my side bodice:

You need to find the same point on the center front, which is a bit trickier. I did this by using my flexible ruler to measure down from the notch to the apex on my side bodice, then on my center front bodice:

Now, this point isn’t really the apex. The apex is really 5/8″ or 2 cm inward because of the seam allowance. This will mark your first pivot point. Mark this point and draw a line down, parallel to the seam line.

You can see in this picture that I drew my line parallel the grain line, not the seam line. This was a mistake. This is one of those times where you need to do as I say, not as I do. You’ll notice in later pictures that I went back and corrected myself. I just somehow forgot to go back and take a photo of the line marked correctly.

Now, you’ll want to draw a line from the apex to the first notch on the neckline. If your pattern does not have a notch here, choose a point an inch or two inward from the seam line.

You’ll also want to draw a line from the apex over to the side seam, about halfway between the notch and the armpit. Again, if you don’t have a notch, choose a point about a quarter of the way down the side seam.

Cutting your pivot lines

You’re now going to, very carefully, cut from the bottom of your bodice, up to the apex, then up to, but not through, the top notch. Leave a small bit of paper at the top notch so that your piece is still hanging together by a thread.

Similarly, cut from the side point to but not through the apex, again leaving this cut so it’s hanging together by a thread of paper.

You’ll see in this picture that I’ve corrected my line from apex to the bottom of my bodice, so it’s now following the seamline instead of the grainline. Yay!

adding width for large breasts

The next step in our princess seam large full bust adjustment is to tape the large side of your piece down to a spare piece of paper. Draw a line parallel to your cut line however many inches from your cut line that you determined you need for your full bust adjustment. In my case, this new line is 1.75″ from the cut piece:

Now, swivel your “hook” to match this line. This will open up a dart on the side seam of your piece. Don’t worry about that just yet. Tape down your “hook.”

Closing the Dart

Now, draw a line from the bottom of the dart you created to the apex point on the seam allowance (not just to the apex point where our cut marks are). On my bodice, this line is very close to the dart line – so much so that it’s hard to see. Yours may look much different, and that does not mean you’ve done anything wrong.

Tape down the bottom of your dart.

Now, cut from the curved side of your pattern piece through that line you drew, stopping at the apex point. Once again, cut to but not through this point.

Now, fold your dart closed. This will essentially move the dart from the side seam to the curved seam of your bodice.

You’ll now want to cut the “hook” piece at the lower notch, to cut the last several inches off. Move this downward to match the bottom of the larger part of your pattern piece, and fill in with scrap paper. Tape into place.

Tape this down, then draw a curve to connect the curved side of your bodice, as shown below. You can use a french curve for this or freehand. I personally freehanded this, even though I had my french curve next to me.

You also need to draw a slightly curved line to fill in the concave on your neckline/armpit area. Again, you can use a french curve to do this or you can choose to freehand it.

Dealing with the Waist

Now, obviously the problem with this full bust adjustment is that it has also added 1.75″ (or however many inches you did for your FBA) to our waistline, which I don’t personally want. The way to deal with this is to remove those same 1.75″ from the waistline.

Mark a dot however many inches inward from the side seam that you added for your FBA. If you added 3″, mark a dot 3″ in from the side seam. If you added 2.25″, mark a dot 2.25″ inward.

Using a french curve or freehanding, draw a gradual line roughly from the notch to the dot you just marked. You want this gradual line to start just below the bust line.

You’ll now cut along this line, and this will be your side seam. I know it looks weird as hell, but it’ll work out. I promise.

Now, I do want to mention that there’s some debate within the sewing community about where it’s best to take this excess. Some dressmakers suggest taking it from the princess seam rather than the side seam, and others suggest splitting this difference, taking some from the side seam and some from the princess seam. From my experiments in pattern drafting, this makes sense to me – the traditional approach in drafting is to distribute excess between multiple places, and when you add extra to one place (here, the princess seam), it also makes sense to remove it from that same place.

I’ve personally always taken the excess from the side seam, and I’ve been happy with the fit. I also note that every princess seam FBA tutorial I’ve seen (such as Curvy Sewing Collective, Megan Nielsen, Seamwork, Deer and Doe, In the Folds) does it this way. However, I’ve heard from some people with larger busts than me who have found this system to not work for them, and have found better success either removing the excess from the princess seam or half from the princess seam and half from the side seam. It’s always a good idea to try out different options and see what works best on your body! I encourage you to experiment 🙂

Altering the Center Front Pattern Piece

Since we added length to the side bodice, we also need to add length to the center front piece. To do this, you’ll first need to use a flexible ruler to measure the side front seam lines on both your side front piece and your center front piece.

Note: This is most accurately done by first removing the seam allowance, then measuring this seamline without the seam allowance. I didn’t remove the seam allowance first, because, as we’ve established, I am lazy. When I went to sew up my dress, this meant this seam didn’t quite “walk” – meaning, one piece was slightly longer than the other. I just trimmed after sewing this seam. But if you want to be super accurate, remove the seam allowance at this step, then add it back afterward.

Now, time for more math: We must figure the difference between the length of the altered side front piece and the length of the unaltered center front piece. For me, my side front seamline was 13″, while the center front was 10-7/8″, leaving me to add 2-1/8″.

You’ll add this amount by marking two lines: one at the apex, and one at the lower dart. Then, you’ll need to divide your total difference between these two spots. This shouldn’t be an even split. I added most of my extra – 1-7/8″ – at the apex, and only a little – 1/2″ – at the dart, and I actually ended up removing some at the dart in a later step.

Cut your piece on your two lines. On a scrap piece of paper, draw two parallel lines however many inches apart as you want to lengthen your center front pattern piece at the apex – in my case, 1-7/8″.

Now, align the bottom edge of the top piece of your center front pattern piece against the top line, and the top edge of your middle piece of your center front to against the bottom line. Tape down.

Repeat this with the extra you’re adding at the dart line. Re-draw the seam lines:

Walking the seams

The last thing I like to do is “walk” the seams. Basically, this means holding the two pieces together and pivoting them to make sure that you can line it up at the top, then that the notches match, then that the bottoms match. At this point, I realized I had added about 1/8″ too much at the bottom notch on my center front piece, so I amended that.

Like measuring your seamlines, this step is best done with the seam allowances removed, but it’s not the end of the world if – like me – you’re too lazy to remove them.

A final check

Okay, the real last thing I like to do is tape the pieces together and hold them up to myself. This helps me to see if the curve is reasonable.

It looked pretty good to me, so I went on my merry way sewing!

Sewing the Rosie – General Tips for Big Boobs

And the full bust adjustment for my big boobs worked! I’m loving the vintage vibes of this dress!

My biggest tip for sewing the Rosie is to try on your dress before you insert the lining. I highly recommend this step. You’ll want to do three things when you do this:

(1) Make sure the curve of your princess seams is correct. I had to change the curve of mine just a tad to lower the apex. This is easier to do before you’ve combined your main bodice and lining.

(2) Check the strap attachment points. The strap attachment points marked on the pattern didn’t cover my bra straps, which I didn’t realize until I’d stitched everything together and understitched. Ugh. Double seam ripping! So, try on your dress before attaching the lining and mark where, for your bra, the straps should be. Mine needed moved in about an inch in both the front and back.

(4) Figure out how long your straps should be. Again, I didn’t do this. I just sewed it up as is, not considering that the straps might not be the right length on me. They were 4.5″ too long. When I unpicked to move the straps, I also shortened them.

Another note: I did not use boning. I just skipped this step entirely. While I had boning in my stash, I felt like the boning wasn’t going to be enough to support my large breasts — I’d still need a bra — so I decided to skip this step for ease. This makes the Rosie a comfy, easy-to-wear summer frock!

Have questions about this full bust adjustment tutorial for large busts? Drop a comment below or or ask on the Sew Busty Facebook group or subreddit.