Bra Size Calculator
Find your US band and cup size from your underbust and bust measurements in inches or centimeters.
Measure the underbust snugly right below your bust, and the bust loosely across the fullest part while wearing an unpadded bra. The band comes from the underbust; the cup comes from how many inches bigger the bust is.
Each inch of difference is one cup: about 1 inch is an A, 2 is a B, 3 is a C, 4 is a D. Cup labels differ by brand and country — a US 32D is roughly a UK 32D but a EU 70E — so use this as a fitting-room starting point.
How it works
A bra size is really two measurements. The band number comes from around your ribcage just under the bust, and the cup comes from how much bigger your bust is than that band.
This uses the common US method: round the underbust to a whole inch (bumping odd numbers up to an even band), then subtract the band from the fullest bust measurement. Each inch of difference is one cup — one inch is an A, two a B, three a C, four a D.
So an underbust of 32 inches and a bust of 35 inches gives a 32 band and a three-inch difference, which is a 32C. Measure in a non-padded bra for the truest read.
Frequently asked questions
Where exactly do I measure?
Measure the band snugly around your ribcage directly under the bust, and the bust loosely across the fullest part while standing straight in an unpadded bra. Keep the tape level all the way around.
What if I'm between sizes?
Bodies rarely land on an exact inch. If the cup difference falls between letters, try both the band down a size with a bigger cup and the band up with a smaller cup — sister sizes often fit similarly.
Do cup letters mean the same everywhere?
No. A US, UK, and EU cup can carry the same letter but map differently, and brands vary too. Use this as your US starting point and try before you commit.