To find your sports bra size, measure your underbust and bust, then check which system the brand uses. Band-and-cup sports bras (like 34D) use the same size as your everyday bra. Letter-sized bras (S, M, L) need the brand’s own chart, checked against both measurements. When you’re between sizes, choose the snugger option for high impact and the roomier one for low-impact comfort.
Step 1: measure
- Underbust: snug around your ribcage, just under your bust. Round up to the next even number for your band.
- Bust: loosely around the fullest part, tape level.
- Cup: the difference between bust and band, one inch per cup (1 = A, 2 = B, 3 = C and so on).
Our bra size calculator does the math and shows your size in US, UK, EU, French and Australian sizing.
Step 2: find the brand’s system
| System | Example | Precision |
|---|---|---|
| Band and cup | 32DD, 36C | High |
| Letter | S, M, L, XL | Approximate |
| Combined | M (34C–34DD) | Medium |
Band-and-cup sports bras are the best bet if your band is small and your cups are full, because letter sizes tie cup volume to band size.
Step 3: convert letter sizes
Letter charts vary, but most brands step up about one band size per letter. A typical pattern:
| Letter | Band often included | Cups often included |
|---|---|---|
| S | 32–34 | A–C |
| M | 34–36 | B–D |
| L | 36–38 | B–DD |
| XL | 38–40 | C–DD |
Treat this as a rough guide only. Our page on bra sizes S, M, L and XL explains why brands differ.
Step 4: decide between sizes
- High impact (running, jumping): pick the smaller band. Support beats roominess, as long as you can breathe deeply.
- Medium impact: pick the size whose chart matches your band.
- Low impact and lounging: pick the larger size for comfort.
- Band fits but cups are tight: move to a brand with band-and-cup sizing, or try your sister size.
Step 5: test the fit
Bravissimo suggests jumping, wiggling and doing high knees in the fitting room. At home, jog on the spot and lift your arms. The band should stay down, nothing should spill and the straps shouldn’t slip. Our full checklist is in how should a sports bra fit.
Sizes change over time
Weight, training, pregnancy and age change your size. Remeasure every six months or so, and whenever a sports bra feels looser or tighter than it used to.
