Bra Size Calculator
Two measurements — underbust and bust — give your band, cup and sister sizes in every major system.
Measurements are calculated locally — nothing is uploaded or stored.
Your size
Enter both measurements and calculate.
How to Measure Yourself
- Underbust: wrap a soft tape snugly around your ribcage, right under the bust, keeping it level.
- Bust: measure around the fullest point of the chest, tape level and not tight — best done in an unpadded bra.
- Use centimetres. Re-measure every year or after weight change — size drifts more than most people expect.
Band Size Chart (underbust in cm)
| Underbust (cm) | US / UK band | EU / CN band | FR | IT | AU |
|---|---|---|---|---|---|
| 58–62 | 28 | 60 | 75 | 0 | 6 |
| 63–67 | 30 | 65 | 80 | 1 | 8 |
| 68–72 | 32 | 70 | 85 | 2 | 10 |
| 73–77 | 34 | 75 | 90 | 3 | 12 |
| 78–82 | 36 | 80 | 95 | 4 | 14 |
| 83–87 | 38 | 85 | 100 | 5 | 16 |
| 88–92 | 40 | 90 | 105 | 6 | 18 |
| 93–97 | 42 | 95 | 110 | 7 | 20 |
| 98–102 | 44 | 100 | 115 | 8 | 22 |
| 103–107 | 46 | 105 | 120 | 9 | 24 |
| 108–112 | 48 | 110 | 125 | 10 | 26 |
Cup Size Chart (bust − underbust)
| Difference (cm) | US cup | UK cup | EU cup |
|---|---|---|---|
| 1.3 ±1.2 | AA | AA | AA |
| 2.5 ±1.2 | A | A | A |
| 5.1 ±1.2 | B | B | B |
| 7.6 ±1.2 | C | C | C |
| 10.2 ±1.2 | D | D | D |
| 12.7 ±1.2 | DD | DD | E |
| 15.2 ±1.2 | DDD/F | E | F |
| 17.8 ±1.2 | G | F | G |
| 20.3 ±1.2 | H | FF | H |
| 22.9 ±1.2 | I | G | I |
| 25.4 ±1.2 | J | GG | J |
| 27.9 ±1.2 | K | H | K |
Frequently Asked Questions
How do I calculate my bra size?
Measure your underbust for the band and your bust at its fullest. The difference between them (about 2.5 cm per cup letter) sets the cup — e.g. 68–72 cm underbust is a 70 EU band, and a 15 cm difference is a C cup: 70C.
What are sister sizes?
Sister sizes share the same cup volume on a different band — 70C, 75B and 65D hold roughly the same volume. If the band feels wrong, move one band size and one cup letter in opposite directions.
Why do US, UK and EU cups differ?
Each system names larger cups differently: a EU E cup is a US DD and a UK DD. Up to D they mostly match; beyond that, compare the difference column rather than the letter.
My size feels wrong — what should I try?
About 80% of support comes from the band. If it rides up, go a band down; if it digs in, go a band up — then flip the cup letter one step the other way. Straps slipping usually means loose band or wrong cup, not loose straps.
Are my measurements uploaded?
No. Everything is calculated locally in your browser — the numbers are never sent, logged or stored.
Calculated size is a starting point — cut, padding and brand change the fit. When between bands, prefer the snugger band and adjust the cup. Band and cup tables use the open MySizeCharts data set (CC BY 4.0). · Size data · Read our fashion coverage