Most commercial patterns are drafted for a B cup. If your bust is larger relative to your frame, the standard fix — sizing up — makes the shoulders, neckline and armholes too big as well, because the whole pattern scales.
A full bust adjustment adds width and length only where it is needed, leaving the shoulders and neckline at your actual size.
How to know if you need one. Measure your high bust — around the chest above the fullest part, under the arms — and your full bust. If the difference is more than about 5 cm, you probably do.
Choose the pattern size by your high bust measurement, then do an FBA to add the difference at the bust. That is the whole principle, and it is why the adjustment exists.
The symptoms it fixes. Drag lines pointing at the bust. A neckline that gapes. Shoulder seams sliding outwards. A hem that rides up at the front. All of these are usually read as “I need a bigger size”, and sizing up makes each of them worse.
The method itself is a slash-and-spread on the front bodice piece: cut along specific lines, spread to add width and length, and true up the resulting dart. It is worth following a diagram rather than a description — but the decision of whether you need one is the part that matters, and that is a measurement.
Questions people actually ask
Does it apply to knits?
Less often, because knits stretch to accommodate. On fitted knit garments with little ease it can still help.
Is there a small bust adjustment too?
Yes, the same method in reverse — choose by high bust and remove width and length at the bust. Less discussed, equally useful.
Last reviewed 2026-08-11