Bra Size Calculator
Band and cup from your measurements in UK, US, EU, FR and AU sizes.
About this tool
Choose inches or centimetres, then enter your underbust measurement, taken snugly around the ribcage, and your bust measurement, taken loosely around the fullest part. The calculator gives your size in UK sizing with US, EU, French and Australian equivalents and lists the sister sizes either side.
How bra size is calculated
The band size is your underbust measurement rounded to the nearest even number of inches, with odd numbers rounded up. The cup size comes from the difference between bust and band: one inch is an A, two a B, three a C, four a D, and so on. An underbust of 31 inches and a bust of 36 inches gives a band of 32 and a 4-inch difference, so 32D. After D, the systems diverge. UK sizing continues DD, E, F, FF, G, GG, H; US sizing usually goes DD or E, DDD or F, G, H; European sizing uses single letters with centimetre bands, where a 32 band is a 70. French bands add 15 to the European figure and Australian bands subtract 22 from the UK figure. Sister sizes, one band size up and one cup down or the reverse, hold the same cup volume, which helps when a band feels too tight or too loose. Measure in a non-padded bra, standing straight, with the tape level all round. Honest limits: this uses the modern method; some brands still use the older plus-four band method, and fit varies by brand and style, so treat the result as a starting point for trying on. The clothing size converter converts dress sizes.
Frequently asked questions
How do I measure my bra size at home?
Measure snugly under your bust for the band and loosely around the fullest part for the bust, keeping the tape level.
What is a sister size?
A size with the same cup volume on a different band: 32D, 30DD and 34C are sister sizes.
Is a UK DD the same as a US DD?
Yes, up to DD the sizes match. After that, UK E is roughly US DDD or F.
Is my data saved?
No. The calculation runs in your browser and nothing is stored or sent.