How should a bra fit? Check yours in a minute
Put on the bra you wear most, tell us its size, and tick what you notice. We'll work out whether the band, the cups or both are off, and give you a size to try next.
Your next size appears here on a fitting card, drawn beside the size you wear now.
- Band level all the way round and comfortably snug
- Cups full and smooth, with the breast tissue inside them
- Center flat against the breastbone
- Wires around the breast, not on it
- Straps stay put without digging in
What brand fit guides say
Four brands' fit advice, paraphrased from their pages opened on 25 September 2026. The fit check uses these directions as starting suggestions.
| Problem | Marks & Spencer | Victoria's Secret (UK) | ThirdLove | SKIMS | Our move |
|---|---|---|---|---|---|
| Band rides up | You might need a smaller band size. | Try a tighter hook or go down a band size if needed. | The band should be parallel to the floor and should not ride up. | Keep the band parallel to the ground when moving your arms; movement may mean it is too big. | Band down |
| Straps dig in | If they are doing all the work, your band may be too big. | They should never dig into your shoulder. | If your straps dig in, your band may be too loose. | Adjust shoulder straps so they are comfortably snug. | Band down |
| Band digs in | – | Try a looser hook. Still tight? Try a larger band and smaller cup size. | – | – | Band up |
| Spilling over | Spilling out? Try a bigger cup. | If you are spilling over, go up a cup size. | A cup that is too small (overflowing). | Spillage on the top or the sides: they may be too small. | Cup up |
| Center lifts off | If it is lifting away, you need a bigger cup size. | – | If the center gore stands away from your body, your cups are too small. | A gap indicates the cup is too small. | Cup up |
| Wires poke | Wires should not poke, rub or press on breast tissue; a different size or style could help. | – | The underwire should not lay on your breast tissue. | – | Cup up, or another style |
| Cups gape | Gaping or creasing? A smaller cup might fit better. | Cups gaping? Go down a size. | A cup that is too big (puckering). | – | Cup down |
Marks & Spencer, Victoria's Secret and ThirdLove all pair a band change with the opposite cup change. Their pages also give worked sister-size examples. Our fit check applies those moves to the size and symptoms you select. A band change keeps the cup-volume category only if the cup letter changes too.
Loose bands, slipping straps and gaping cups
Choose only the signs you can see in your bra. Slipping straps do not have their own checkbox; use the band and cup checks below.
Bra band too loose
A band that rides up may be too loose. Try a tighter hook first on a bra you already wear. If that does not help, try one band down and one cup letter up to keep the same cup-volume category, for example 34D to 32DD.
Check my size for a loose band
Bra straps falling down
Adjust the straps so they sit comfortably, then check the band and cups. ThirdLove says falling straps may mean the cups are too big, while a moving band may be too loose. If the band rides up, select that symptom. If the cups gape or wrinkle, select gaping cups instead. Slipping alone does not tell this checker which size to change.
Bra cups too big or gaping
Gaps or wrinkles can mean the cup is too big, though the style can also affect the fit. With a comfortable band, try one cup letter down on the same band, for example 34D to 34C. If that still does not fit, try another style rather than keep sizing down.
How the fit check decides
The same engine as the calculator and sister-size chart, with the same conversion limits. A brand may not make every size it can calculate.
Band first
The band does most of the lifting (ThirdLove puts the straps at about 10% of the work). A band that rides up or leaves the straps doing the work is too loose: we move one band down. Going down a band shrinks the cups too, so we move the cup letter up one to keep the same volume. That is a sister size: 34D becomes 32DD.
Then the cups
Spilling or a lifting center can mean a bigger cup is needed: the checker suggests one letter up on the same band. Wires pressing on tissue can also call for another style. For gaping or wrinkles, it suggests one letter down. When both the band and cups need changing, a 34D that rides up and spills becomes 32DD for the band, then 32E for the cups (US 32DDD).
When the signs disagree
If you tick a band that is both too loose and too tight, or cups that both spill and gape, we don't guess. Mixed signs can call for a fit or style check rather than another size change. The result flags the conflict and keeps that part of your size; it may still change the other part if those signs agree.
Before you buy a new size
- Keep the band level. For a new bra, ThirdLove recommends the loosest hook, leaving room to tighten it as it stretches; Victoria's Secret recommends starting on the middle hook. For a bra you already wear, its advice is to try a tighter hook before a smaller band.
- Lean forward and settle the breast tissue into each cup, then stand up and check again.
- Loosen the straps: if the bra stays put without them, the band is doing its job.
A fit check can't see your shape. If two sizes in a row still fail, a fitter can tell you what we can't. For the size you should start from, use the calculator.
Quick answers
How should a bra fit?
The band sits level and snug and provides support. ThirdLove recommends the loosest hook on a new bra so it can be tightened as it stretches; Victoria’s Secret starts on the middle hook. The cups hold all the breast tissue with no spilling or gaping, the center between the cups lies flat on the breastbone, the wires sit around the breast rather than on it, and the straps stay put without digging in.
Why does my bra ride up at the back?
The band may be too loose. On a bra you already wear, try a tighter hook as Victoria’s Secret suggests. If it still rides up, try one band down and one cup letter up to keep the cup volume, for example 34D to 32DD.
Why do my bra straps dig in?
Usually because the band is too loose and the straps are carrying the weight. Loosen the straps; if the band then rides up, go down a band and up a cup.
What does it mean if the center of my bra does not touch my chest?
A lifting center can mean the cups are too small. Try one cup letter up on the same band; if the wires still press or rub, a different style may fit better.
Next steps
- Bra size calculatorTwo methods side by side, and why they disagree
- How to measureBand, bust and the leaning check, step by step
- Sister sizesThe whole chart, and what to try when the band rides up
- UK to US converterAny size in any of six systems
- Bra size chartUS sizes in inches, then UK, EU, FR, AU and Japan on one grid
- Cup sizes guideWhat a cup letter means, and why it changes by band
- Plus size brasBands 40 and up, cups DD and up: sizing, fit and styles, with the numbers
- Brand size chartsVictoria's Secret, ThirdLove, Wacoal, SKIMS, M&S and Freya, read side by side
- Small bra sizesBands 28 to 32 and AA to B cups: what the charts cover
- Largest bra sizeWhere the size chart ends, and where brands stop
- Swimsuit size by bra sizeBra size to bikini top, from brand charts
- Bra stylesCompared by fit: 13 cuts from full cup to bralette
- 30DSister sizes, conversions and fit notes
- 32BSister sizes, conversions and fit notes
Sources
Each source was opened and checked on the date shown, or on 25 September 2026. Where sources disagree, the page says so instead of picking one silently.
- Marks & Spencer, "How to Measure Bra Size": fit checks; sister sizing; a tape gives a rough starting point (opened 25 September 2026)
- Victoria's Secret UK, "Measure Your Bra Size": band = snug underbust rounded to the nearest even number; fit fixes; sister table (opened 25 September 2026)
- ThirdLove, "Bra Size Calculator & Chart": bands 32 to 44, cups AA to H with half cups; 6 synthetic pairs submitted to the calculator; 5 result pairs recorded (opened 25 September 2026)
- SKIMS, "Bra Size Guide": underband/overbust grid and US/UK/EU/AU cup table disagree above DD; grid skips DDD (opened 25 September 2026)
- White J, Scurr J. Evaluation of professional bra fitting criteria for bra selection and fitting in the UK. Ergonomics 2012;55(6):704-711: 45 women; the traditional method overestimated band and underestimated cup
- McGhee DE, Steele JR. Optimising breast support in female patients through correct bra fit. J Sci Med Sport 2010;13(6):568-572: 104 women in Australia; 85% in ill-fitting bras