How to Measure Your Bra Size Correctly
Most people wear the wrong size because they guess instead of measure. With a soft tape measure and two numbers — your band and your bust — you can find your size in a couple of minutes, then convert it to US, UK, EU or AU sizing.
Step by step
- 1 Measure your band size
Wrap a tape measure snugly around your ribcage, directly under your bust, keeping it level all the way around. Take the measurement in inches while exhaling. This is your underbust measurement.
- 2 Measure your bust size
Measure around the fullest part of your bust, with the tape level and not too tight. Wear an unpadded bra or none at all for accuracy.
- 3 Find your band
Round your underbust to the nearest even number — that's your US/UK band size (e.g. 33 in rounds to band 34).
- 4 Calculate your cup
Subtract your band measurement from your bust measurement. Each inch of difference is one cup size: 1 in = A, 2 in = B, 3 in = C, and so on. Enter both numbers below to get the exact size.
Bra size calculator
Enter your band (underbust) and bust measurements to get your size and its international equivalents:
Uses the standard difference method. Brands vary a lot — treat this as a starting point and try sister sizes if the fit is off.
FAQ
How is cup size calculated?
Cup size is the difference between your bust and band measurements, in inches. 1 inch ≈ A, 2 ≈ B, 3 ≈ C, 4 ≈ D, 5 ≈ DD/E, 6 ≈ F, and so on. The band number and cup letter together make your size, e.g. 34C.
What are sister sizes?
Sister sizes have the same cup volume but a different band. Going down a band and up a cup (e.g. 34C → 32D) keeps roughly the same cup capacity. Useful when a band feels too tight or loose but the cups fit.
Should the band be tight?
The band does most of the support and should be firm and level around your body — you should just fit two fingers under it. A band that rides up at the back is too big.
Why do UK and EU cup letters differ?
Above a D cup the scales diverge: US uses DD, DDD/F, G…; UK uses DD, E, F, FF, G…; EU uses E, F, G continuously. A US DD is roughly a UK DD and an EU E. Use the converter to translate.
How often should I re-measure?
Re-measure every 6–12 months, or after weight changes, pregnancy, or if bras stop fitting. Body shape shifts more than people expect.
→ Bra size calculator & international chart (US / UK / EU / AU)