Bra size calculator
Measure under your bust and around the fullest part, type both numbers, and get your band and cup size in US and UK sizing, with the sister sizes to try.
Enter both measurements to see your size.
Measure in a soft unpadded bra or none, standing upright. A calculator gives a starting size, not a verdict: bra sizing varies by brand, so check the fit with the four checks in the guide below.
How do you calculate your bra size?
Measure snugly under your bust for the band and around the fullest part of your bust for the cup. Round the band measurement to the nearest even number in inches, because band sizes come in even numbers: 32, 34, 36 and so on. The cup is the difference between the two measurements, about one inch per cup letter: 1 inch is an A, 2 inches a B, 3 inches a C, 4 inches a D. The cup letter only means something in relation to its band, so a D on a 30 band and a D on a 38 band are different volumes.
What are sister sizes?
Sister sizes hold about the same cup volume on a different band. Going up one band size means going down one cup letter, so 36C, 34D and 32DD are sisters. If a band feels too tight but the cup fits, try the larger band with the smaller cup. If the band rides up at the back, try the smaller band with the larger cup.
Why does the band matter more than the cup?
The band does most of the support, not the straps. A band that is too loose is the most common fitting mistake, and it usually pairs with a cup that is too small. The center panel should sit flat against your sternum; if it floats away from your chest, the cup is too small. Your size can change with weight, hormones, pregnancy and age, so measure again once or twice a year.
The full answer: How to find your bra size. All our tools: see the list.
