Small Bust Adjustment
Excess fabric at the bust, or the pattern gaps away from your chest? If your full bust is less than 2 inches larger than your high bust (A cup or smaller), you need a Small Bust Adjustment. Enter your measurements and we'll calculate the overlap.
How the SBA works
Commercial patterns are drafted for a B cup (roughly 2 inches difference between high bust and full bust). If your difference is less than 2 inches — an AA or A cup — there is more fabric at the front bust than your body needs. The result: excess fabric that pools at the bust, a hemline that dips in front, or a dart that sits too high.
A Small Bust Adjustment removes this extra fabric using a slash-and-overlap technique — the inverse of an FBA. The same two cut lines are used, but instead of spreading the pattern open, you overlap the edges inward. The existing dart gets smaller to match. Pattern size is still determined by your high bust measurement.
How to take these measurements
High Bust
Wrap the tape directly under your armpits, above the bust. Parallel to the floor, snug but not tight. This sets your pattern size.
Full Bust
Wrap at the fullest part of your bust, parallel to the floor. For a small bust, the difference between these two measurements will be small — often less than 1 inch.
Do you actually need an SBA?
Subtract your high bust from your full bust. Patterns are drafted for a 2 in / 5 cm difference, so anything below that means there is more fabric in the front bodice than your body fills:
| Full bust minus high bust | Pattern cup | Typical SBA |
|---|---|---|
| 2 in / 5 cm | B — pattern default | None needed |
| 1 1/2 in / 4 cm | A/B | 1/4 in |
| 1 in / 2.5 cm | A | 1/2 in |
| 1/2 in / 1.5 cm or less | AA | 3/4 in or more |
The tell-tale signs are fabric that stands away from the chest above the bust, a wrinkle that folds down from the armhole, a side dart that points above where your bust actually is, or a front hemline that hangs longer than the back.
How to do a darted SBA, step by step
- Trace the front bodice in your high bust size and mark the apex, roughly 1 in past the printed dart point.
- Draw line 1: from the hem, parallel to the grainline, up through the apex, then angling to the armhole about a third of the way up from the underarm.
- Draw line 2: from the apex into the middle of the side dart.
- Cut both lines, leaving a paper hinge at the armhole and at the dart tip.
- Overlap — do not spread — by the calculated amount, keeping the cut edges parallel. The side dart shrinks as you overlap. Tape flat.
- Level the hem. Overlapping raises the lower front, so the hem now rides up. Slash horizontally below the dart and drop that section until the hem is straight, filling the gap with paper.
- True the dart to its new, smaller point, stopping about 1 in short of the apex. If the dart has become tiny, consider removing it entirely and easing that small amount into the side seam.
- Walk the side seam against the back piece and re-check the armhole curve.
Common SBA mistakes
Sizing down instead of adjusting. Picking a smaller size to fix bust bagging shrinks the shoulders, armhole, and back too — parts that already fit. Size by high bust and take the excess out only where it exists.
Removing the dart entirely. Unless your measurement difference is essentially zero, you still need some shaping. A small dart is not a mistake to be eliminated; it is what keeps the bodice from hanging straight down from the chest.
Ignoring the hem. An SBA shortens the front at the center. Skipping the levelling step leaves the front hem visibly higher than the back.
Confusing an SBA with a narrow chest. Fabric pooling above the bust can also come from broad shoulders or a wide upper chest drafted into the pattern. If the excess is at the armhole rather than at the bust apex, an upper chest adjustment is the right fix.
Related tools
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