Bra Size Calculator
Find your estimated band size, cup size, and bra fit using simple bust and underbust measurements.
Calculate Your Bra Size
Enter your measurements to get your estimated bra size instantly.
Your Estimated Bra Size
Use this result as a starting point for bra shopping and fitting.
How to Measure Your Bra Size
Measure your underbust snugly around your ribcage, directly under your bust. Then measure around the fullest part of your bust while keeping the tape level and relaxed.
You can use inches or centimeters. For best results, stand naturally and avoid pulling the tape too tight.
How Bra Size is Calculated
Your band size is estimated from your underbust measurement and rounded to the nearest even number. Your cup size is based on the difference between your full bust and your band size.
A larger difference means a larger cup size. This calculator uses inches internally for cup logic, even when you enter cm.
What Are Sister Sizes
Sister sizes are alternate bra sizes with a similar cup volume. If your usual band feels too tight or too loose, a sister size can help you get a better fit.
For example, if your size is 34D, you can also try 32DD or 36C depending on the fit you prefer.
Bra Size Calculator FAQs
How do I know my bra size?
Measure your underbust and full bust, then compare the difference to a cup size chart.
Can I measure at home?
Yes, a soft measuring tape is usually enough to estimate your starting bra size at home.
What is cup size?
Cup size is based on the difference between your bust measurement and your band size.
What are sister sizes?
Sister sizes are nearby sizes with similar cup volume but different band sizes.
Is this calculator accurate?
It gives a strong starting estimate, but brand sizing and bra style can still affect your final fit.