Bra Size Calculator
Calculate your bra size (band and cup) from your underbust and bust measurements.
- Free to use
- Accurate results
- No registration required
- Works on all devices
Your result
34C
Your bra size
AI explanation
Formula
Band size = underbust rounded to the nearest even whole number; cup size = bust − underbust, rounded, mapped to a letter in 1-inch stepsWorked example
34-inch underbust, 37-inch bust
| Field | Value |
|---|---|
| Underbust measurement (inches) | 34 |
| Bust measurement (inches) | 37 |
| Band size | 34 |
| Cup size | C |
| Your bra size | 34C |
Assumptions
- Uses the common US direct-band sizing method — some brands and regions use slightly different conventions (e.g. adding 4-5 inches to underbust for "old style" UK sizing), which can give a different band number for the same measurements.
- Measurements should be taken while wearing a well-fitting, non-padded bra for the most accurate result.
Frequently asked questions
How do I measure underbust and bust correctly?
For underbust, wrap the tape snugly (but not tight) directly under your bust, keeping it level all around. For bust, wrap the tape around the fullest part of your bust, keeping it level and not compressing — both are best measured while wearing a well-fitting, non-padded bra.
Why do my calculated size and a brand's fitting differ?
Sizing conventions vary by brand and country (US, UK, and EU sizing all differ), and cut, style, and fabric also affect fit — treat this as a starting point and adjust based on how a specific bra actually fits.
What if my measurement doesn't fall on a whole number?
The calculator rounds to the nearest whole number automatically — enter your exact measurement (including half-inches) for the most accurate rounding.