Measure twice and use the average if the numbers differ, and remeasure after weight changes, pregnancy or a new workout routine.
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
Should the tape be tight for the underbust?
Snug but not painful. The band carries most of the support, so it should be firm.
Where do I measure for the bust?
Around the fullest part, usually across the nipples, with the tape level across your back.
What if my underbust is an odd number?
Modern sizing rounds to the nearest even band, so 31 rounds up to 32 and 33 rounds to 34. Try both nearby bands in store.
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.