Sports Bra Sizes: Size Chart, Impact Levels and How a Sports Bra Should Fit
Sports bras are sized three ways: letters, band and cup, or a mix such as M (C/D). This page converts your everyday bra size to each system and explains how impact level and construction change the size you need.
Letter-sized sports bras typically map to bra sizes as XS = 30-32 band, A-B cup; S = 32-34, A-C; M = 34-36, B-D; L = 36-38, B-D; XL = 38-40, C-DD. For running and other high-impact sports, a band-and-cup sized sports bra (for example 34D) fits more precisely than a letter size, especially above a C cup.
- Size S
- 32-34 band, A-C
- Size M
- 34-36 band, B-D
- Size L
- 36-38 band, B-D
- Band fit
- firmer than daily bra
On this page
Sports bra size chart: bra size to letter size
Find your usual band and cup, then the letter size in that row. Where your size sits in two rows, the band decides: choose the size whose band range includes yours.
| Letter size | Band | Cups | Bust (in) | Bust (cm) |
|---|---|---|---|---|
| XS | 30-32 | A-B | 31-34 | 79-86 |
| S | 32-34 | A-C | 33-37 | 84-94 |
| M | 34-36 | B-D | 36-40 | 91-102 |
| L | 36-38 | B-D | 38-42 | 97-107 |
| XL | 38-40 | C-DD | 41-45 | 104-114 |
| XXL | 40-42 | C-DD | 43-47 | 109-119 |
The bust column is band plus cup (one inch per cup), the same arithmetic as the bra size chart. Brands shift these ranges, so compare your bust and underbust with each maker's own chart before ordering.
Three sizing systems
| System | Example | Fits best | Limitation |
|---|---|---|---|
| Letter size | M | A-C cups, low to medium impact | One size covers about 6-8 bra sizes, so the fit is approximate |
| Combined | M (C/D) | Cups above average for the band | Still a single band per letter, often without hooks |
| Band and cup | 34D | D cup and above, high impact | Less stretch, so the measurement must be right |
Letter-sized pullover bras have no hook band to adjust, so the fixed band size has to be right from the start. Band-and-cup sports bras usually have three or more rows of hooks, and you can fit them on the loosest row and tighten as the elastic relaxes.
Impact level: match the bra to the activity
| Impact | Activities | Construction to look for |
|---|---|---|
| Low | Yoga, Pilates, walking, stretching, strength training without jumping | Compression pullover, wide band, letter sizing is fine |
| Medium | Cycling, hiking, skiing, gym classes, dance | Compression or encapsulation with a firm band; adjustable straps |
| High | Running, HIIT, jumping, tennis, basketball, horse riding | Encapsulation or combination, band-and-cup sizing, hook closure, wide padded straps |
Researchers at the University of Portsmouth's Research Group in Breast Health have shown that breasts move up and down, side to side and in and out during running, not only vertically. A bra that controls all three directions has to hold each breast separately, which is why high-impact bras for larger cups use molded or seamed cups instead of a single compression panel.
Compression vs encapsulation
Compression (one panel)
- Presses both breasts against the chest wall
- Usually letter-sized and pulled over the head
- Works well for A-C cups at any impact
- Fit check: firm everywhere, no bulging at the top or sides
Encapsulation (separate cups)
- Supports each breast in its own cup, like an everyday bra
- Sized by band and cup; often with hooks and adjustable straps
- Best for D cups and above, and for high impact
- Fit check: cups smooth, no gaping, underband flat to the ribs
Combination bras use separate cups inside a compression outer layer. They suit most cup sizes for high impact and are usually sized by band and cup or by combined sizes.
How to check sports bra fit
- Band: snug and level. Fit two fingers under it, no more. Raise both arms overhead: the band should not slide up.
- Cups: all breast tissue inside, with no spillover at the top, sides or under the arms, and no wrinkles or empty space.
- Straps: one finger under each; they should not dig in or slip off. Racerbacks and crossbacks are less likely to slip on narrow shoulders.
- Movement test: jog on the spot or jump for 20-30 seconds. If you feel bounce, try a firmer band size or a higher-impact model before changing cups.
- Breathing test: take a full deep breath. A band you cannot breathe against is too small, even for compression.
Red lines under the band or at the strap edges after a workout usually mean the band is too loose (it moves) rather than too tight. Try one band size smaller with one cup size larger, the sister size, before switching models.
Sports bras for different needs
- Large cups (DD and above): choose band-and-cup sizing, encapsulation and hook closures. Front-zip and front-hook styles make a firm bra easier to put on.
- Small cups: compression in letter sizes is usually enough even for running; padded or molded cups add shape if wanted.
- Pregnancy and nursing: sizes change from month to month. Nursing sports bras have clips or pull-aside cups; see the nursing bra size guide.
- Everyday comfort: soft letter-sized styles overlap with bralettes but have a firmer band.
For the rest of a training outfit, the leggings size chart and the athletic wear size guide cover bottoms and tops.
Frequently asked questions
Should a sports bra be a size smaller than a regular bra?
Often the band, not the cup. Sports bras rely on a firm band, so many people go down one band size and keep the same cup volume (a 34C may fit a 32D sports bra). Compression bras in letter sizes should feel firm but still allow a full breath.
What size sports bra for a 36DD?
In letter sizes a 36DD is at or beyond the top of most L ranges, which often stop at D. Choose a band-and-cup sports bra in 36DD, or a combined size such as L (DD/E) if the brand offers it.
How tight should a sports bra be?
You should fit about two fingers under the band and one under each strap, and the band should not ride up when you raise your arms. Jump or jog on the spot: breasts should feel held, without the band slipping.
What do sizes like M (C/D) mean?
Combined sizes split one letter size by cup. M (C/D) fits a band of about 34-36 with C or D cups, while M (A/B) fits the same band with smaller cups. They fit better than letter sizes alone if your cup is above average for your band.
When should I replace a sports bra?
When the band no longer feels firm on its tightest setting, the fabric stays stretched after washing, or you notice more movement than when it was new. Heat from tumble drying wears elastic faster.