Free Bra Measurement Calculator (Accurate 2026 Bra Size Guide)

Cup overflow is almost always a sign your cup size is too small — but the shape matters too. If tissue is escaping from the top, try going up one cup size first. Still happening? You might need a style with more projection or fuller coverage. Demi cups are notorious for this with fuller shapes because they simply cut across the breast instead of containing it properly.

Slipping straps are almost never actually a strap problem. When your band is too loose it rides up your back and changes the strap angle completely. Before you mess with the straps, try tightening the band first. If your straps are already fully tightened and still slipping, you need a smaller band size — not shorter straps.

A band that creeps up means it is too big, plain and simple. Your band should sit level all the way around — parallel to the floor front and back. This matters because 80% of your bra's support comes from the band, not the straps. Try one band size down and the difference will be immediate.

Pain after a few hours means something is wrong with the fit. Most common causes are a band that is too tight, underwire sitting on breast tissue instead of behind it on the chest wall, or cups that are the wrong shape for your breast type. Run through our fit check above to find exactly which one is causing your pain.

A floating gore — the center bridge between the cups — means the cups are not fully containing your breast tissue. This usually happens when the cup is too small or the bra style does not match your breast shape. If you have close-set or projected breasts a plunge or balconette style often solves this immediately.

Underwire that digs in at the sides is sitting on breast tissue rather than behind it against your ribcage. This happens when the cup is too small or the wire width is too narrow for your breast root. Try going up a cup size first. The wire should sit completely flush against your ribcage with no breast tissue on top of it.

You need exactly two measurements. First measure snugly directly under your breasts — that is your underbust. Then measure loosely across the fullest part of your chest — that is your overbust. Take each measurement twice and average them. Never measure with a bra on. Then put both numbers into our calculator above for your exact size in every sizing system worldwide.

Sister sizes share the exact same cup volume but with a different band size. Go up one band and down one cup — the actual space inside the cup stays identical. So 34DD has the exact same cup volume as 32F and 36D. This is useful when your size is sold out, when a brand runs small, or when you are between sizes.

Because there is no universal standard anywhere in the lingerie industry. Every brand uses its own block, its own grading system, and its own interpretation of what a cup should look like. A 34C from Marks and Spencer fits nothing like a 34C from Savage X Fenty. Our brand decoder page breaks down exactly how each major brand runs and what size to order.

Every six to eight months with regular wear. Signs it is time: the band rides up even on the tightest hook, your straps are maxed out and still slipping, or the cups have gone flat. Washing on a gentle cycle and always air drying will extend the life of your bras significantly. Machine heat is what kills them fastest.

The band numbers are exactly the same but the cup letters split after D. UK goes D then DD then E then F then FF then G. US goes D then DD then DDD or F then G. So a UK 34E is the same cup volume as a US 34DDD. Our calculator handles all of this automatically so you never have to think about it.

Shape matters as much as size. Full on top shapes do well in full coverage or balconette styles. Projected shapes need real cup depth so plunge styles usually work best. East-west shapes benefit from center-pull designs that bring tissue forward. Wide-set shapes need a wider center gore. Use our breast shape guide for a complete matched recommendation based on your specific shape.