Two Numbers.
One Accurate Cup Size.
Your cup size isn't a fixed number it's relative to your band. Enter your band size and bust measurement to get an instant, accurate cup size, based on the same difference method professional fitters use.
- ✓ Results in under a minute, no sign-up needed
- ✓ Works in inches or centimetres
- ✓ Covers AA through J cup
Calculate your cup size
Measure with a soft tape, standing naturally, over a well-fitted (or no) bra.
How We Calculate Your Cup Size
Cup size is the difference between your bust (the fullest point of your chest) and your band size, rounded to the nearest inch. Each inch of difference moves you up one cup letter a 1" difference is an A cup, 2" is a B cup, and so on. Because the letter depends entirely on your band, the same bust measurement can be a completely different cup size on a different band that's why band size should always be calculated first.
Step-by-Step: How to Measure Your Bust
- Wear a well-fitted, non-padded bra (or none at all). Padding will inflate your bust reading.
- Wrap a soft measuring tape around the fullest part of your bust, usually across the nipple line.
- Keep the tape level and relaxed not pulled tight, not loose enough to sag.
- Read the number, then subtract your band size to find the difference or just enter both above and let the calculator do it.
Bust-to-Band Difference Chart
Use this chart to see exactly how the difference between your bust and band maps to a cup letter.
| Difference | Cup Size |
|---|---|
| Less than 1" | AA |
| 1" | A |
| 2" | B |
| 3" | C |
| 4" | D |
| 5" | DD |
| 6" | DDD / E |
| 7" | F |
| 8" | G |
| 9" | H |
| 10" | I |
Frequently Asked Questions
Why is my cup size different on every website?
Because cup size is relative to band size, and calculators use slightly different rounding rules. Always calculate band size first, then cup size, for a consistent result.
Is a bigger cup letter always a bigger bust?
Not necessarily. A 30D and a 38D have very different bust measurements the letter only tells you the difference from the band, not the absolute size.
What if my difference is more than 10 inches?
Cup letters beyond J (K, L and so on) exist but aren't standardised across brands it's best to check the specific retailer's size chart at that range.