Utility Loft → Bra Size Converter
Bra Size Converter
Calculate your size from measurements, or convert a size you already know between US, UK, EU, French, and Australian sizing — with your sister sizes shown instantly.
Measure the underbust snugly around your ribcage, and the bust around the fullest part, both level to the floor.
Enter your measurements above to get your bra size in every standard.
Cup letters above D vary by brand — always check the label's own size guide for the perfect fit.
Popular pages
Band size conversion
The band is the ribcage number. US and UK share the same inch numbers; Europe and France use centimeter bands; Australia uses dress-style numbers.
| US / UK | EU | France / Spain | Australia / NZ |
|---|---|---|---|
| 28 | 60 | 75 | 6 |
| 30 | 65 | 80 | 8 |
| 32 | 70 | 85 | 10 |
| 34 | 75 | 90 | 12 |
| 36 | 80 | 95 | 14 |
| 38 | 85 | 100 | 16 |
| 40 | 90 | 105 | 18 |
| 42 | 95 | 110 | 20 |
| 44 | 100 | 115 | 22 |
| 46 | 105 | 120 | 24 |
Cup size conversion
Cup letters by the bust-minus-band difference. US and UK match up to D, then diverge.
| Bust − band | US | UK | EU | Australia |
|---|---|---|---|---|
| 0" | AA | AA | AA | AA |
| 1" | A | A | A | A |
| 2" | B | B | B | B |
| 3" | C | C | C | C |
| 4" | D | D | D | D |
| 5" | DD | DD | E | DD |
| 6" | DDD | E | F | E |
| 7" | G | F | G | F |
| 8" | H | FF | H | FF |
| 9" | I | G | I | G |
| 10" | J | GG | J | GG |
Conversions are standard approximations. Cup lettering above D differs between brands, so treat larger cups as a starting point.
Frequently asked questions
How do I calculate my bra size?
Take two measurements with a soft tape. First the band: measure snugly around your ribcage directly under the bust. Then the bust: measure loosely around the fullest part. Your band size is the underbust rounded to the nearest even number, and your cup comes from the difference between bust and band — about one inch per cup letter. Enter both above and the tool does the math.
What is a sister size?
Sister sizes are bra sizes with the same cup volume but a different band. Going down a band (e.g. 34C → 32D) keeps the same cups on a tighter band; going up a band (34C → 36B) keeps them on a looser band. They're useful when a band feels off but the cups fit, or when your exact size is out of stock.
Why don't US and UK cup sizes match?
They agree up to a D cup, then use different letters for the same volume. A US DDD is a UK E; a US G is a UK F. European sizing uses yet another sequence (and centimeter bands). This converter maps all of them from one US size.
Should I use the +4 method for my band?
The older method added 4–5 inches to the underbust to get the band. Most modern fitters skip it and use the underbust measurement directly (rounded to an even number), which usually gives a firmer, better-supporting band. This tool uses the modern method; if bras feel too tight, try the next band up.
How often should I re-measure?
Re-measure after any noticeable weight change, pregnancy, or when bras stop fitting well — and at least once a year. Body shape shifts, and a band that's ridden up or cups that gap are signs it's time to re-check.