Under half an inch of difference is an AA cup. Past a K (UK) or O (US) the standard chart ends and full-bust brands size differently.
How the bra size calculator works
BraSizeCalc uses the inch-based method most US and UK brands publish. The band is your underbust rounded to the nearest even inch (modern method), or, if you choose the traditional method, rounded to the nearest inch with 4 added for an even number and 5 for an odd one. The cup is the bust measurement minus the band, rounded to the nearest inch, with one letter per inch. Centimetre measurements are divided by 2.54 first. EU bands are 70 for a 32 and go up 5 for each band size; French bands are EU + 15; Australian bands are the inch band minus 22.
Cup letters by bust minus band
| Difference | US | UK | EU |
|---|---|---|---|
| under ½ in | AA | AA | AA |
| 1 in | A | A | A |
| 2 in | B | B | B |
| 3 in | C | C | C |
| 4 in | D | D | D |
| 5 in | DD | DD | E |
| 6 in | DDD | E | F |
| 7 in | G | F | G |
| 8 in | H | FF | H |
| 9 in | I | G | I |
| 10 in | J | GG | J |
| 11 in | K | H | K |
| 12 in | L | HH | L |
| 13 in | M | J | M |
| 14 in | N | JJ | N |
| 15 in | O | K | O |
Band sizes
| Underbust (in) | Band US/UK | EU | FR | AU |
|---|---|---|---|---|
| 27–29 | 28 | 60 | 75 | 6 |
| 29–31 | 30 | 65 | 80 | 8 |
| 31–33 | 32 | 70 | 85 | 10 |
| 33–35 | 34 | 75 | 90 | 12 |
| 35–37 | 36 | 80 | 95 | 14 |
| 37–39 | 38 | 85 | 100 | 16 |
| 39–41 | 40 | 90 | 105 | 18 |
| 41–43 | 42 | 95 | 110 | 20 |
| 43–45 | 44 | 100 | 115 | 22 |
Brands cut differently, so treat the result as a starting size and check the fit: the band should be level and firm, the centre gore should sit flat and the cups should not gap or spill. Sizes past DD vary most between brands.
Frequently asked questions
How many inches is a D cup?
A D cup is a 4 inch difference between bust and band, about 10 cm.
What cup is a 6 inch difference?
UK E or US DDD (also sold as F), EU F.
Is a D cup the same on every band?
No. Cup volume grows with the band, which is why sister sizes exist.
Is BraSizeCalc free?
Yes, with no sign-up or ads.
Are my measurements saved or sent anywhere?
They are saved in this browser only and never leave your device.