Bust Size Calculator
Bust size calculator works out Bra size and Band size from Underbust (ribcage) measurement, Bust measurement and Measurement unit. The default figures on this page give bra size of 32DDD; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
4 steps
- Underbust 32 in, bust 38 in.
- +0 method: round 32 to the nearest even inch - band 32.
- Bust minus band = 38 - 32 = 6 in, which is 6 whole cup steps above AA.
- US / North America labelling: band 32, cup DDD - 32DDD.
Sister sizes (same cup volume)table
The same bra in other systemstable
Figures from bra sizing systems, checked 31 August 2026. Its 4 worked examples are re-run on every release, last on 15 September 2026. What changed · how reference data is kept current
Sources and references
3 sources
What the bust size calculator calculates
Works out band size and cup letter from underbust and bust measurements, by either the +0 or the traditional +4 method, and converts the result into US, UK, EU, French, Italian, Australian and Japanese labelling.
How to use this bust size calculator
Enter Underbust (ribcage) measurement, Bust measurement, Measurement unit and Band sizing method. Bra size updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Bra size, Band size and Cup.
The method follows Bra size - consumer measurement methods and the international band/cup equivalence charts, EN 13402, Size designation of clothes and JIS L4006 (Japan) and KS K9404 (South Korea) dress size standards.
What you can compare
Change one input at a time to see how it affects Bra size, Band size and Cup. The inputs you can vary are Underbust (ribcage) measurement, Bust measurement, Measurement unit, Band sizing method and Size labelling system.
Understanding Bra size, Band size and Cup
Bra labelling is an industry convention, not a standard: cut varies between brands and even between styles from one brand. Treat this as a starting size to try on, not a measurement.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How do I determine my bust size?
Works out band size and cup letter from underbust and bust measurements, by either the +0 or the traditional +4 method, and converts the result into US, UK, EU, French, Italian, Australian and Japanese labelling. Open “How this is worked out” beside the result to see each step for your own figures.
What is a 36 inch bust?
Works out band size and cup letter from underbust and bust measurements, by either the +0 or the traditional +4 method, and converts the result into US, UK, EU, French, Italian, Australian and Japanese labelling. On this page it is computed from Underbust (ribcage) measurement, Bust measurement and Measurement unit and shown as Bra size, Band size and Cup.
Is a 42 inch bust big?
Works out band size and cup letter from underbust and bust measurements, by either the +0 or the traditional +4 method, and converts the result into US, UK, EU, French, Italian, Australian and Japanese labelling. On the figures this page opens with — underbust (ribcage) measurement 32 and bust measurement 38 — the bra size is 32DDD. Put your own figures in their place and the working updates beside the result.
What's my bust size if I'm a 34C?
It needs Underbust (ribcage) measurement, Bust measurement, Measurement unit, Band sizing method and Size labelling system. Nothing else is required, and the figures stay in your browser.
What information do I need for the bust size calculator?
You need Underbust (ribcage) measurement, Bust measurement, Measurement unit, Band sizing method and Size labelling system. The page opens with default figures that give bra size of 32DDD, so you can see the scale before entering your own.
What does this bust size calculator show?
It shows Bra size, Band size, Cup, Band, US/UK inches, Bust minus band, Cup step above AA, Sister sizes (same cup volume) and The same bra in other systems, with the working and any warnings for your entries.