👙 Bra Size Calculator

You need a soft measuring tape. Measure your under-bust snugly around your ribcage just below your breasts — this gives your band measurement. Then measure around the fullest part of your bust. Enter both measurements into our calculator above. Wear a non-padded bra or no bra for the most accurate results.

Sister sizes are bra sizes that contain the same cup volume but with a different band size. For example, 34C, 36B and 32D are all sister sizes — they have the same cup volume. Going up a band size means going down a cup letter, and vice versa. Sister sizes are useful when your exact size is hard to find.

Bra sizing is not standardised across brands. Different manufacturers use slightly different measurements and construction methods. This is why you may be a 34C in one brand and a 34D in another. Always try bras on before buying, or check the brand's specific size guide. Our calculator gives you a starting point based on standard UK sizing guidelines.

UK and US bra sizes share the same band sizes but differ in cup sizes from DD upwards. In the UK, sizes go DD, E, F, FF, G, GG, H. In the US, the equivalent sizes are DD, DDD/E, F, G, G, H, H. Our calculator automatically converts your size to US and all other major international sizing systems.

EU bra band sizes are different from UK sizes. A UK 32 band is EU 70, UK 34 is EU 75, UK 36 is EU 80 — each UK band size adds 5 to get the EU equivalent. Cup sizes also differ from DD upwards. Our calculator automatically converts your size to EU and all other major international sizing systems.

A correctly fitting bra should have a band that sits horizontally and snugly around your body — you should be able to fit two fingers underneath. The cups should fully encase your breast tissue with no spillage or gaping. The underwire should sit flat against your ribcage and fully surround your breast tissue. Straps should sit comfortably without digging in or slipping.

Our calculator supports both inches and centimetres. UK bra sizing is traditionally done in inches, but you can use whichever unit you prefer — just make sure both measurements use the same unit. Select your preferred unit at the top of the calculator before entering your measurements.

It is recommended to check your bra size every 6–12 months, or whenever you notice a significant change in weight, after pregnancy, after breastfeeding, or if your current bras no longer feel comfortable. Many lingerie specialists offer free professional fittings.