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A Full Bust Adjustment Tutorial for Kitty, A Dress With a Centre Front Dart

A Full Bust Adjustment Tutorial for The Kitty Dress, a dress with a Centre Front Bust Dart.


There I said it…does that little phrase strike fear into your heart? FBA – a full bust adjustment tutorial. It’ll be fine….but get comfy…and maybe get some snacks….this is a looong post. Oh, and right up front, I’m going to say – a toile (or two) is going to be your friend for this one, people.

There are actually a gazillion (I counted) tutorials for a Full Bust Adjustment (FBA), all of them great if you have a bust dart at the side seam, or no dart, or princess seams. But I can’t find one for a dress with a dart at the centre front seam like KITTY, but it’s the same principal – slash and spread. And honestly, I have actually never done a Full Bust Adjustment for myself (I’m a B cup) and the patterns I’ve produced for industry for the great British High Street are also drafted for a B cup.

So, while knowing the theory, I had no go-to, tried and personally tested method to recommend. Which has led to a lot of research into this tutorial…and why it’s taken me so long to finish it.

At this point, I would like to say a BIG shouty THANK YOU! to Rachel, Queen of the French Dart Shift, who very kindly confirmed my research for me, when after looking at every FBA tutorial in the Universe I became, what can only be described, as bust blind!


Sewing patterns are generally (and there are exceptions) drafted to accommodate a B cup. All Maven Patterns are drafted with a B cup. Unfair I know, but unfortunately, it’s just not possible for us to produce a pattern that will keep every body shape happy, the variations are limitless! Sorry.

So, great if you are a B cup, but not so much if you are bigger (or smaller). In which case you might need to do a Full Bust Adjustment – FBA (or a Small Bust Adjustment – SBA). Today I’m concentrating on the FBA, as that’s the one I’m getting asked about.

Small Bust Adjustment side note: A SBA is basically the same process, but involves overlapping the pattern to reduce instead of spreading the pattern to increase the bust cup size. If you need a Small Bust Adjustment, there will be too much fabric over the bust area, and your bodice will be too long at the centre front.

How do you know if you need a full bust adjustment? Your toile may be gaping at the armhole, will have drag lines pointing to the bust, and probably looks a bit ‘strained’ over the bust, your girls just look a little squashed in there!

What you need is more width and length to your pattern at the right place – to go over and around a fuller cup. The idea is to do this without messing about with your armhole and sleeve too!

You may have already done a FBA and have a good idea of how much to add, feel free to jump straight down to the fun slash and spread bit!

WHICH CUP SIZE ARE YOU? – Let’s take some measurements

Measure yourself while wearing the appropriate underwear. If you are going to wear a padded bra under your dress, go put one on first – it will make a difference to the fit.

Importantly, your cup size for a sewing pattern is not the same as your bra cup size. (I’m a B for a pattern, and wear a D bra)


Measure your HIGH bust across your back, under your armpits and above your bust.

Then measure your FULL bust, at the fullest part of your bust.

Note these measurements and the difference between them.

Difference of 1 ½” (4cm) = A cup (SBA)

Difference of 2″ (5cm) = B cup

Difference of  3” (6.5cm) = C cup (FBA)

Difference of 4” (10cm) = D cup  (FBA)

Difference of 5” (12.5cm) = DD cup (FBA)


If you are above a B cup you’ll probably need to do a FBA and should select your size by using your HIGH bust measurement in place of your FULL bust measurement.

This is the most common and popular method, by far, because it will give a better fit in the shoulders and neck area, then you just do a FBA and adjust for a fuller bust. If, on the size chart, you have a size 16 full bust, but a high bust measurement of a size 12, chances are the shoulders of a size 16 pattern will be completely out of proportion for you! You may need to adjust or blend between sizes for hips and waist.


HOW MUCH TO ADD? The Million Pound Question

There isn’t a definitive answer to this bit, there are more options than those I’ve listed here, but for clarity I’ve chosen these two**. There is not one way to do this alteration (or any alteration). It can be a little test and see, and a lot of getting to know your OWN body and how you like a garment to fit on you.

Take these measurements as a guide. You’ll need to toile and test and tweak your alteration, maybe more than once. Like I said…a toile is your best friend – the fabric doesn’t lie! Also consider the look of the garment, a looser fitting garment might not need as much adding as a very fitted garment. Or you might just decide you want more/less ease and adjust your FBA accordingly.

It is very much trial and error the first couple of times, but once you know what works for you, it’ll be so worthwhile.

**For those interested I have an APPENDIX at the very end of the tutorial with ‘Other Thoughts on The How Much To Add?’ question.

METHOD 1 | Cut open your toile



Make a quick toile (just the body, don’t bother with sleeves, collar etc) and mark your bust point. CUT open your toile and see how much you need. With the Kitty dress having a Centre Front seam you can just open up here and see how much needs to be added at the bust.

Remember when you are adjusting the pattern you are working with HALF a body front, so if you have 1 ½” (4cm) gap at you CF, you’ll need to divide it by 2 and add ¾” (2cm) to each side.

With other styles you could cut a cross in the fabric at your Bust Point / Apex, let it spread open and then measure how much extra you need. (For a SBA, instead of slashing a cross, pin the excess out of the bust)

I like this slash and spread and see what you need method. Pay attention to the neck and shoulders of your toile, and see if they fit or if a size smaller/bigger would look better on you. Or you may need to do a shoulder alteration as well.

METHOD 2 | Maths

Take your FULL bust measurement and minus your HIGH bust measurement = TOTAL amount to add, DIVIDE TOTAL by 2 = the amount to be added to pattern (as we are altering HALF a body front)

For example:

My imaginary friend MARGO has a 34” (86.5cm) high bust, her full bust is 37” (94cm) which is a difference of 3” (7.5cm) making her a C cup.

High bust measurement of 34” places Margo as a UK size 10 on the Maven Body Measurement Chart, so she selects that size. (Her full bust of 37” would put her between a UK 12/14)

The difference between Margo’s HIGH BUST and FULL BUST is 3” (7.5cm), this is the amount she needs to add in TOTAL as a FBA, so she adds 1 ½”( 3.8cm) to half a dress front pattern.

METHOD | The Fun Slash and Spread Bit!









TRACING WHEEL (optional, but very useful)

Find the BUST POINT (also called the APEX)


Using a copy of your front pattern mark on the seam allowances so you know where the stitch line is.

Draw a line through the centre of the bust dart, and extend it  1” (2.5cm) the dart tip. That is the bust point of the pattern.

Mark your Bust point (BP) on the pattern (either transfer it from your toile or just hold the pattern up against yourself). (Tips how to measure your BP here)

Compare your BP with the pattern BP. You may need to lengthen/shorten your dart so it aligns with your BP.

If the dart is too high for your bust, don’t worry about lowering the dart yet as the FBA will make the dart drop a little anyway ¼” to ½” (6mm – 12mm) and we can adjust this later. If you are very low busted, you can lower the dart a little now, and then go back and get it perfect later.


1. LINE 1: Draw a line from the BUST POINT (BP) right down to the hem, parallel with the grain line. Draw a line from the BP to ⅓ of the way along the armhole.

2. LINE 2: Draw a line from BP towards CENTRE FRONT LINE (CF) through centre of the dart.

3. LINE 3: Draw at a right angle from line 1 to intersect CF (not crucial where, I went half way between waist and dart).

4. LINE 4: Draw a line from BP slightly above bust dart intersecting CF

5. Draw in the WAIST: Use the notch on the CF and draw a line straight across to the side seam at a right angle to the grainline.

CUT THE LINES  | slash and spread.

FULL BUST ADJUSTMENT TUTORIAL 6. Cut along LINE 1. Start at the hem and cut towards the armhole. Cut UP TO stitch line but NOT through it. Cut from OUTSIDE of the pattern up to the same point on the armhole stitch line, leaving a 3mm hinge of paper.

*if you hinge your armhole from the outside edge of the pattern instead of the stitch line, your armhole increases in length and then your sleeve won’t fit properly.

7.  Cut along LINE 2 through centre of bust dart towards the BP, leaving a hinge at BP.

8.  Mark sections A, B, C & D as in diagram


9. Place some paper behind your pattern piece. Anchor down section A with tape or pins. Spread open LINE 1 the amount you need to add for your FBA, pivoting the pattern from the hinges. Keep LINE 1 parallel with each other and the grain line. Let front section slide upwards  and allow the bust dart to open wider to keep pattern flat.

Note how the waist is staggered and CF is now too short. Tape section A and B down. Slide a separate piece of paper behind the dart and tape, attaching top dart section back to lower dart in section C.  

*When you are taping, be aware that sections C and D still need to move.


10. Cut open lines 3 and 4, no need to leave a hinge this time.

11. Slide section D down so the waist is level again. This creates some extra length in the bodice below the dart.  


12. We want a little of that extra length above the bust dart, so slide section C down halfway into that space created at LINE 3, so it is now evenly distributed above and below the dart. Fill any gaps with paper and tape everything down.


13. Redraw your bust dart. Remember, the tip of a bust dart is usually 1” (2.5cm) from the BP, but this can change depending on you – it could be ½” (1.2cm) if you are small busted and up to 3” (7.5cm) if you have a fuller bust.

14. Fold your bust dart as if you are stitching it, with the bulk of the dart downwards, and true your CF seam (redraw your CF line so it is a smooth line). Use a tracing wheel or cut along the edge of your pattern to create your dart extension. 

14. Now you get to toile your alteration! You can pin the paper pattern together and try it on to check the dart position first. I like to toile after a major alteration and prefer to see it in fabric.

You may still need to lower your dart, and if you need a little more detailed explanation of truing the pattern and creating a bust dart extension, my Lower a Bust Dart Tutorial will help!

APPENDIX | Other Thoughts on The How Much To Add question?

I really did do a lot of research for this tutorial, and came across these solutions too.

If we go back to METHOD 2: Maths (The Full bust – High Bust = TOTAL, divided by 2 = amount to add to pattern method) for a minute – which I know for a fact works in the real world – imaginary friend Margo would be adding a total of 3” to her bust area .

At this point I carried on researching because that seems an awful lot of fabric to add in, when Margo’s boobs are only 1” bigger than mine, and I happily wear a UK size 10 with no FBA.

Personally, my HIGH bust is 34”, FULL bust 36”, difference of 2”. While I don’t need a FBA I do in fact wear the size 10, based on my High Bust, for Kitty and The French Dart Shift. I have a regular sized frame across the shoulders and the back and, on me, I prefer the fit in the shoulders of the size 10 rather than that of the size 12. Crucially I also prefer to wear a garment with a more fitted bust area and without too much ease (boxy and shapeless does me NO favours). These things are all worth considering when deciding how much to add.

So….METHOD 2: Maths / OPTION 2: My theory was to take the difference of 3″ and take off the 2” already included in the pattern for a B cup. This gives us a 1” difference (½” on each side) to use for a FBA. This also ties in with several tutorials that have said add ½” per cup size. The Craftsy FBA tutorial says ½” for C cup, increasing by ¼” per cup size. I eventually found this tutorial by Grainline with the same theory. So I’m probably not completely bonkers and if you find you’re adding too much it might be worth a go.

METHOD 3: Don’t use your High Bust to select your size. 

That title is not strictly true…Take your high bust measurement and add 2” and select that size to use as you base pattern size, (because that would be the size of your bust if you were actually a B cup, before doing the FBA.) As a pattern cutter, this makes perfect sense!

EXAMPLE: Back to imaginary Margo….34” high bust, 37” full bust and a difference of 3”

34” high bust  + 2” for a B cup = 36” means Margo selects a size 12.

37” Margo’s full bust measurement – 36” Maven size 12 body measurement = difference of 1” to add (½” each side).

With Method 3 Margo will be wearing a dress with shoulders and neck one size larger than if she selected her size using Method 2. Margo might want to take this into consideration when she decides which size pattern to use.

You made it to the end, well done! Now, go forth and adjust those busts! Many thanks to my imaginary friend Margo for the use of her imaginary body.