Bra Band & Cup Size Calculator

How to use this tool

1. Measure snugly around your ribcage directly under the bust — this is the underbust.
2. Measure loosely around the fullest part of the bust, keeping the tape level.
3. Enter both numbers and select your unit, then press Convert.
4. Try the sister size if the band rides up or the cup gapes.

How to measure correctly

Measure the underbust firmly — the band carries most of the support. Measure the overbust loosely without compressing tissue, ideally while wearing an unpadded bra.

• Use a soft tailoring tape rather than a rigid ruler.
• Keep the tape parallel to the floor the whole way round.
• Breathe out normally instead of holding your breath.
• Take each measurement twice and use the average.

Understanding these sizes

Sizing labels come from three different families: alpha labels such as S, M and L, numeric labels such as US 8 or EU 38, and measurement labels such as a 32 inch waist. Converting between them means moving between systems that were standardised separately, which is why offsets are conventions rather than exact rules.

Bra fitting, maternity, plus size, tall and other specialised sizing helpers. Once you know your own measurements in centimetres, any chart in any region becomes readable, and a converter simply saves you the arithmetic.

Size conversion chart