Bra Size Calculator
Most people are wearing the wrong bra size. Grab a soft tape measure and two numbers, and find yours in seconds.
- Your US band and cup size
- Sister sizes to try
- A guide to measuring correctly
How to measure your bra size
- Underbust: measure snugly around your ribcage, right under your bust, keeping the tape level
- Bust: measure loosely around the fullest part of your bust, without compressing it
- Measure wearing an unpadded bra or no bra, standing straight
Your band is your underbust rounded to the nearest even number. Each inch of difference between your bust and your band is one cup size.
Bra cup size chart
| Bust minus band | US cup | UK cup |
|---|---|---|
| 1" | A | A |
| 2" | B | B |
| 3" | C | C |
| 4" | D | D |
| 5" | DD / E | DD |
| 6" | DDD / F | E |
| 7" | G | F |
Why not add 4 inches?
Older methods added 4 or 5 inches to the underbust to get the band. That method came from when bras were less stretchy, and it usually gives a band that's too big and a cup that's too small. Most modern fitters use the underbust as-is.
Sister sizes
Sister sizes have the same cup volume on a different band. If 34C fits in the cup but the band is loose, 32D is its sister size. Sizes vary by brand, so use your result as a starting point. Comparing other measurements? Try the Height Percentile Calculator.
Frequently asked questions
Is my bra size the same in every brand?
No. Use your calculated size as a starting point and adjust for each brand.
How often should I measure?
Every 6 to 12 months, and after weight change, pregnancy or new exercise routines.
What are signs my bra doesn't fit?
The band rides up, the straps dig in, the cups gape or overflow, or the center doesn't sit flat.