Free Bra Size Calculator (Accurate 2026 Guide)

Cup overflow usually means your cup size is too small, but it can also be a shape issue. If tissue escapes from the top or sides, try going up one cup size first. If that doesn't fix it, look for a style with more projection or fuller coverage — demi cups tend to cut across the bust and cause this in fuller shapes.

Slipping straps are almost never a strap problem — they're a band problem. When your band is too loose, it rides up and takes the strap angle with it. Try tightening the band first before adjusting straps. If your straps are fully tightened and still slip, you likely need a smaller band size.

A band that creeps up means it's too big. The band should sit level all the way around — parallel to the floor, not higher at the back than the front. 90% of the bra's support comes from the band, so this is critical. Try one band size down and see if it stays put.

Pain after a few hours is your body telling you the fit is off somewhere. Common causes: band too tight, underwire sitting on breast tissue instead of the chest wall, or cups that are the wrong shape for your breast type. Run through our fit check to pinpoint exactly what's wrong.

A floating gore means the cups aren't containing your breast tissue properly — usually because the cup is too small or the style doesn't match your breast shape. If you have close-set or projected breasts, a plunge or balconette style often works better than a full-cup bra.

Underwire that digs in at the sides means it's sitting on breast tissue rather than behind it. This happens when the cup is too small or the wire width doesn't match your breast root. Try a wider-wire style or go up a cup size — the wire should sit flush against your ribcage, not your breast.

You need two measurements: underbust (snug, right under your breasts) and overbust (across the fullest point, tape relaxed). Take both twice and use the average. No bra on — ever. Then plug them into our calculator above for your exact size in any sizing system worldwide.

Sister sizes share the same cup volume but with a different band. Go up a band, down a cup — the volume stays identical. So 34DD = 36D = 32F in terms of cup space. This is incredibly useful when your exact size is sold out, or when a bra runs small or large in a particular brand.

Because there's no universal standard. Every brand uses its own block, its own grading, and its own interpretation of cup depth. A 34C in M&S fits nothing like a 34C from Savage X Fenty. Our brand decoder page explains the major offenders and what size to order in each.

Every 6 to 8 months with regular wear — sooner if the band has stretched out or the underwire is poking through. Signs it's time: the band rides up even on the tightest hook, the straps are maxed out, or the cups have lost their shape. Washing on a gentle cycle and air-drying extends lifespan significantly.

The band numbers are the same, but the cup letters diverge after D. In the UK, it goes D → DD → E → F → FF → G. In the US, it goes D → DD → DDD/F → G. So a UK 34E is a US 34DDD — same cup volume, different letter. Our calculator handles all conversions automatically.

It depends on your shape, not just your size. Full-on-top shapes do well in full-coverage or balconette styles. Projected shapes need depth in the cup — plunge styles often work well. East-west shapes benefit from center-pull designs. Use our breast shape guide for a full matched recommendation.