Bra size calculator and converter
Measure around your ribcage under the bust and around the fullest part of the bust, enter both and get a starting size. Or pick a size in one country's system and see it in the others. Brands fit differently, so treat the result as a place to start.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- From measurements: pick inches or centimetres, enter your underbust and your bust, and read the band and cup in US and UK sizing, with the equivalent in EU, FR and AU.
- Convert a size: choose the system your size is in, pick the band and cup, and see it in every system.
Method
- Band = underbust rounded to the nearest even inch (no “+4”). 31 in rounds up to 32.
- Cup = bust − underbust in whole inches: 1 in = A, 2 = B, 3 = C, 4 = D, 5 = DD, 6 = DDD (US) or E (UK), 7 = G (US) or F (UK) and so on. A difference below half an inch is AA.
- Centimetres are converted at 2.54 cm to the inch.
| US/UK band |
EU |
FR |
AU |
| 30 |
65 |
80 |
8 |
| 32 |
70 |
85 |
10 |
| 34 |
75 |
90 |
12 |
| 36 |
80 |
95 |
14 |
| 38 |
85 |
100 |
16 |
Worked example
Underbust 30 in and bust 34 in. Band: 30 is already even, so 30. Difference: 34 − 30 = 4 in, which is cup D. The size is 30D (US and UK), 65D in EU and 80D in France.
Tips
- Measure standing, relaxed and without a heavily padded bra.
- If the band rides up, go down a band size and up a cup, and the other way if it digs in.
- Sports bras, maternity bras and bras from different countries each fit a little differently.
- This is general information, not medical advice. If you have pain, a lump or skin problems, talk to a doctor.
Frequently asked questions
How do I measure my bra size?
Wear a lightly padded or unlined bra. Measure around your ribcage directly under the bust with the tape level and snug, then around the fullest part of the bust without pulling the tape tight. Use the same unit for both.
How does this calculator choose the band and cup?
The band is your underbust measurement rounded to the nearest even inch, with no 4 inches added. The cup comes from the difference between bust and underbust in whole inches. 1 inch is A, 2 is B, 3 is C, 4 is D and 5 is DD (E in EU and French sizing).
Why does another calculator give a different size?
Methods differ. Some add 4 or 5 inches to the underbust, and brands cut their sizes differently. This tool uses the straight underbust method and says so. Always try the size on.
What are sister sizes?
Sizes with the same cup volume, such as 34C, 32D and 36B. When the band goes up by one size (2 inches), the cup letter goes down by one. If a band is too tight or loose, a sister size may fit better.
Is the size conversion exact?
The band and cup follow the standard conversion charts: US and UK bands match, EU is 5 cm per band step, and FR is 15 higher than EU. Cup letters differ above DD, for example US DDD is UK E. Brands may still label sizes differently.