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Full Bust Adjustment
A Full Bust Adjustment adds extra room in the bust area without changing the fit of the shoulders, neckline, or upper chest. It helps the garment sit smoothly over your curves and prevents pulling, gaping, or strain across the bust.
This adjustment can be done before making a toile if you already know you need it, or after your toile if the fit makes it clear that more room is needed.
What this adjustment is
Choose your pattern size based on your high bust, then add room with an FBA.
A Full Bust Adjustment increases the width and length over the bust so the fabric can travel smoothly over fuller curves. It does this by:
Adding width at the bust.
Adding length so the front doesn’t lift.
Keeping the neckline, shoulders, and armhole in place.
It’s one of the most transformative adjustments for dressmakers.
When you need this
adjustment
You may need an FBA if:
your bust measurement is larger than your high bust size
garments pull or strain across the bust
the front hem lifts or tilts upward
buttons gape
armholes feel tight at the front
darts point too high or too low
the waist seam sits higher in the front
Why this issue happens?
Most patterns are drafted for a B‑cup (sometimes C‑cup).
If your bust is fuller than the draft:
the fabric has to travel further over the bust
the front becomes too short
drag lines radiate from the bust apex
the waistline lifts at the front
An FBA adds the space the pattern didn’t include.
Before You Begin:
Choosing Your Cup Size
We covered how to choose your sewing cup size — and how to measure it accurately — in the Fitting Foundations module.
If you’re unsure which cup size your pattern is drafted for, or how to calculate your own sewing cup size, revisit that lesson here:
👉 Flat Pattern Adjustments - Bust Adjustments
This will help you decide whether you need a Full Bust Adjustment, a Small Bust Adjustment, or no adjustment at all.
If the pattern doesn’t list a drafted high bust measurement
Some pattern companies only list the full bust the pattern is drafted for (e.g., “Drafted for a 34" bust”).
If the high bust isn’t shown, you can estimate it using a simple, universal rule:
👉 Subtract 2" (5 cm) from the listed full bust measurement.
This gives you a working drafted high bust measurement, which helps you:
choose the correct starting size
understand how the pattern was proportioned
decide whether you need an FBA or SBA
Example:
Pattern bust: 96 cm
Drafted high bust estimate: 96 − 5 = 91 cm
If your own high bust is close to 91 cm, you’re a good match for that size.
If your high bust is larger, you’ll likely need an FBA.
How to know how much to add
The amount you add in your Full Bust Adjustment depends on how much bigger your full bust is compared to the bust the pattern was drafted for in your chosen size.
It is not based on the difference between your own high bust and full bust.
Here’s the clear, step‑by‑step method.
STEP 1
Choose your pattern size using your high bust
Patterns are drafted for a specific cup size (often a B‑cup).
This means the full bust measurement on the size chart assumes a certain high‑bust‑to‑full‑bust difference.
So:
Measure your high bust.
Choose the pattern size whose full bust measurement is closest to your high bust measurement.
This gives you the size that will fit your shoulders, neckline, and upper chest correctly.
STEP 2
Find the pattern’s full bust measurement for that size
Look at the size chart and note the full bust measurement for the size you just selected.
If the pattern doesn’t list a drafted high bust, you already added the correct section earlier:
Estimate the drafted high bust by subtracting 2" (5 cm) from the pattern’s full bust.
But for calculating the FBA amount, you only need the pattern’s full bust for your chosen size.
STEP 3
Compare your full bust to the pattern’s full bust
Now calculate the difference:
Your full bust−Pattern full bust (your size)=extra room needed
This tells you how much extra space the pattern needs to fit your bust comfortably.
STEP 4
Divide by 2
Because the pattern piece represents half your body, divide the total difference by 2.
This gives you the amount to add to the pattern piece itself.
STEP 5
Full Example
Your high bust: 96 cm
Your full bust: 102 cm
The pattern is drafted for a B‑cup, which assumes a 5 cm difference between high bust and full bust.
Choose your size by high bust
You look at the size chart and choose the size where the pattern full bust = 100 cm, because:
Pattern drafted full bust (100 cm) − assumed 5 cm = drafted high bust 95 cm, which is the closest to your 96 cm high bust.
This gives you the correct size for your shoulders and upper chest.
2. Compare your full bust to the pattern’s full bust for that size
Your full bust: 102 cm
Pattern full bust (your chosen size): 100 cm
102−100=2 cm total extra needed
3. Divide by 2 (because the pattern is half the body)
2÷2=1 cm per side
👉 You will add 1 cm in your FBA on the pattern piece.
How to do an FBA on a bodice with only a bust dart
This method adds extra room through the existing bust dart while keeping the neckline, shoulders, and overall silhouette unchanged.
1. Mark the bust apex
Use the pattern’s marking or your own apex position.
2. Draw your cutting lines
Draw:
a line from the bust apex to the side seam (through the dart)
a line from the bust apex to the armhole (ending 1 cm before the seam allowance to create a hinge)
a vertical line from the waistline up to the bust apex
3. Cut along the lines
Cut:
up the vertical line
through the apex
toward the armhole (leave a hinge)
through the dart to the side seam
4. Spread the pattern
Spread the pieces apart by the amount you calculated.
This will:
increase width
increase length
enlarge the dart
Tape the pieces onto scrap paper.
5. Keep the centre front straight
Ensure the centre front remains perfectly vertical.
7. True the seams
Check:
the side seam is smooth
the waist seam is level
the armhole curve is unchanged above the hinge
6. Redraw the dart
Your dart will now be larger. Redraw:
dart legs
dart point (2.5–4 cm from apex)
fold line
1. Mark the bust apex
Use the pattern’s marking or your own apex position.
2. Draw your cutting lines
Draw:
a straight line from the bust apex to the side seam, passing through the centre of the bust dart
a straight line from the bust apex to the waistline, passing through the centre of the waist dart
a straight line from the bust apex to the armhole, stopping 1 cm before the cutting line to create a hinge
3. Cut and spread
Cut each line, leaving the hinge at the armhole intact.
4. Spread the pattern
Open the cut sections until the gap equals the amount you need to add.
Both darts will enlarge.
5. Tape the pieces down
Place scrap paper behind the openings and tape everything securely.
6. Redraw both darts
Make sure:
both darts point directly toward your bust apex
both darts end 2.5–4 cm before the apex
the dart legs are even and smooth
7. True the seams
Smooth the waistline, side seam, and the upper part of the armhole.
1. Work on the side front piece
This is the piece that contains the bust curve.
2. Mark your bust apex
Use the pattern’s marking or your own apex position.
3. Draw your cutting lines
Draw:
a straight line from the bust apex down to the waistline
a straight line from the bust apex to the armhole, stopping 1 cm before the cutting line to create a hinge
4. Cut along the lines
Cut both lines, leaving the hinge at the armhole.
5. Spread the pattern
Open the cut sections until the gap equals the amount you need to add.
6. Tape the pieces down
Slide scrap paper underneath the openings and tape the pieces securely.
7. Redraw the princess seams
Smooth the curved sea so if flows naturally over the bust.
8. True the seams
Walk the seams to ensure the side front and centre front still match.
1. Mark your bust apex
Use the pattern’s marking or your own apex position.
2. Draw your cutting lines
Draw:
a vertical line from the waistline straight up to the bust apex
a straight line from the bust apex to the armhole, stopping 1 cm before the cutting line to create a hinge
a horizontal line from the bust apex to the centre front
3. Cut along the lines
Cut each line, leaving the hinge at the armhole.
4. Spread the pattern
Open the cut sections until the gap equals the amount you need to add. A dart will appear — this is expected.
5. Tape the pieces down
Place scrap paper behind the openings and tape everything flat.
6. Rotate the dart closed
Swing the lower section of the pattern until the dart closes. This moves the shaping into the side seam so the bodice remains dart‑free.
7. Smooth the side seam
Redraw the side seam so it is smooth and natural.
8. True the seams
Check the hem and armhole for smoothness.
How to do an FBA on a bodice with only a bust dart
This method adds extra room through the existing bust dart while keeping the neckline, shoulders, and overall silhouette unchanged.
1. Mark the bust apex
Use the pattern’s marking or your own apex position.
2. Draw your cutting lines
Draw:
a line from the bust apex to the side seam (through the dart)
a line from the bust apex to the armhole (ending 1 cm before the seam allowance to create a hinge)
a vertical line from the waistline up to the bust apex
3. Cut along the lines
Cut:
up the vertical line
through the apex
toward the armhole (leave a hinge)
through the dart to the side seam
4. Spread the pattern
Spread the pieces apart by the amount you calculated.
This will:
increase width
increase length
enlarge the dart
Tape the pieces onto scrap paper.
5. Keep the centre front straight
Ensure the centre front remains perfectly vertical.
7. True the seams
Check:
the side seam is smooth
the waist seam is level
the armhole curve is unchanged above the hinge
6. Redraw the dart
Your dart will now be larger. Redraw:
dart legs
dart point (2.5–4 cm from apex)
fold line
1. Mark the bust apex
Use the pattern’s marking or your own apex position.
2. Draw your cutting lines
Draw:
a straight line from the bust apex to the side seam, passing through the centre of the bust dart
a straight line from the bust apex to the waistline, passing through the centre of the waist dart
a straight line from the bust apex to the armhole, stopping 1 cm before the cutting line to create a hinge
3. Cut and spread
Cut each line, leaving the hinge at the armhole intact.
4. Spread the pattern
Open the cut sections until the gap equals the amount you need to add.
Both darts will enlarge.
5. Tape the pieces down
Place scrap paper behind the openings and tape everything securely.
6. Redraw both darts
Make sure:
both darts point directly toward your bust apex
both darts end 2.5–4 cm before the apex
the dart legs are even and smooth
7. True the seams
Smooth the waistline, side seam, and the upper part of the armhole.
1. Work on the side front piece
This is the piece that contains the bust curve.
2. Mark your bust apex
Use the pattern’s marking or your own apex position.
3. Draw your cutting lines
Draw:
a straight line from the bust apex down to the waistline
a straight line from the bust apex to the armhole, stopping 1 cm before the cutting line to create a hinge
4. Cut along the lines
Cut both lines, leaving the hinge at the armhole.
5. Spread the pattern
Open the cut sections until the gap equals the amount you need to add.
6. Tape the pieces down
Slide scrap paper underneath the openings and tape the pieces securely.
7. Redraw the princess seams
Smooth the curved sea so if flows naturally over the bust.
8. True the seams
Walk the seams to ensure the side front and centre front still match.
1. Mark your bust apex
Use the pattern’s marking or your own apex position.
2. Draw your cutting lines
Draw:
a vertical line from the waistline straight up to the bust apex
a straight line from the bust apex to the armhole, stopping 1 cm before the cutting line to create a hinge
a horizontal line from the bust apex to the centre front
3. Cut along the lines
Cut each line, leaving the hinge at the armhole.
4. Spread the pattern
Open the cut sections until the gap equals the amount you need to add. A dart will appear — this is expected.
5. Tape the pieces down
Place scrap paper behind the openings and tape everything flat.
6. Rotate the dart closed
Swing the lower section of the pattern until the dart closes. This moves the shaping into the side seam so the bodice remains dart‑free.
7. Smooth the side seam
Redraw the side seam so it is smooth and natural.
8. True the seams
Check the hem and armhole for smoothness.
Before you cut fabric, check
Did you add the correct amount?
Is the centre front still straight?
Does the dart point stop short of the apex?
Are the dart legs even?
Does the side seam match the back bodice?
Is the armhole unchanged above the hinge?
Common mistakes to avoid
Adding too much length but not enough width
Letting the centre front tilt
Placing the dart point too close to the apex
Forgetting to true the side seam
Changing the armhole shape
Skipping the toile