Bra Size Calculator
Enter two measurements: around your ribcage just under the bust (snug) and around the fullest part of the bust. You get a starting size in US, UK and EU sizing and the two sister sizes to try next to it.
Free, no sign-up. What you enter stays in your browser: it is not saved or sent to HerFound. Reviewed .
Units
Around the ribcage directly under the bust. Pull the tape snug and keep it level.
Around the fullest part of the bust. Keep the tape level and do not pull it tight.
Enter your underbust and bust measurements to see your size.
How it works
For US and UK sizes the calculator uses the modern method most fitters now use. Band = your snug underbust measurement in inches, rounded to the nearest even number (an odd whole number such as 31 rounds up to 32). Nothing is added to it. The older method added 4 or 5 inches to the band, and a 2012 study in the journal Ergonomics found that it overestimated band size and underestimated cup size.
Cup = bust minus band, rounded to the nearest inch, with one cup size for each inch. US cups run AA (less than 1 inch), A, B, C, D, DD/E, DDD/F, G, H, I, J, K. UK cups run AA, A, B, C, D, DD, E, F, FF, G, GG, H. The two systems share the same band numbers and the same letters up to D, then differ.
The EU size is the same fit converted the way international size charts do it. The band goes up 5 for every band size: 28 is 60, 30 is 65, 32 is 70, 34 is 75, 36 is 80. The cup is the same step in the EU letter sequence, which has no double letters: D, then E, F, G, H. So UK 32DD (US 32DD/E) is EU 70E.
Some European brands size by a different rule, from the underbust in centimetres and a cup that starts later, which gives a looser band and a smaller letter for the same body. If a brand publishes its own chart, use that. Sister sizes hold about the same cup volume on a different band: one band down with one cup up, and one band up with one cup down. For 34C they are 32D and 36B.
What it cannot tell you
- Sizes vary by brand and by style. Some brands, mainly in the US, still add inches to the band, and cup letters above D are not used the same way everywhere. Check the brand's own size chart before you buy.
- A tape measure cannot see breast shape, how full the breasts are at the top or bottom, or how far apart they sit. Two people with the same measurements can need different sizes. A fitting with a trained fitter is better than any calculator.
- Your size is not fixed. It can change across the menstrual cycle, in pregnancy and while breastfeeding, with changes in weight and with age, so measure again from time to time.
- This gives a size to start trying on, not a verdict. The right bra is the one where the band sits level and firm, the cups hold the whole breast and nothing digs in.
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Common questions
To measure your bra size at home, take two measurements with a soft tape. Measure snugly around the ribcage directly under the bust, then around the fullest part of the bust with the tape level and not tight. The band comes from the first number and the cup from the difference between the two.
No, the modern bra fitting method does not add 4 inches to the band. The band is the snug underbust measurement rounded to the nearest even number. Adding 4 inches is an older method that some brands still use, and a 2012 study found it overestimates band size and underestimates cup size.
A sister size is a bra size with about the same cup volume on a different band. Go down one band and up one cup, or up one band and down one cup. The sister sizes of 34C are 32D and 36B, and they are useful when the cup fits but the band feels too loose or too tight.
Yes, a US DD and a UK DD are usually the same cup, the fifth cup size. The systems differ after that: the next cup is DDD or F in the US and E in the UK. A US 34DDD/F is about a UK 34E, though brands do not all follow the same sequence.
To convert a US or UK bra size to an EU size, change the band and then the cup. The band goes 28 to 60, 30 to 65, 32 to 70, 34 to 75, 36 to 80, 38 to 85. EU cups have no double letters, so they run AA, A, B, C, D, E, F, G, H. UK 34DD and US 34DD/E are both EU 75E.