Bra Size Calculator
Uses the traditional US "band + 4/5" method (underbust rounded to the nearest whole number, plus 4 if even or 5 if odd) — different sites use different formulas, which is exactly why results vary between calculators. Sister sizing and brand fit still vary; treat this as a starting point, not a guarantee.
Free bra size calculator using the traditional US band-and-cup method — enter your underbust and bust measurements to get an estimated size, with the formula clearly shown.
How it works
- Choose inches or centimeters
- Enter your underbust (band) and bust (fullest point) measurements
- See your estimated band size, cup size, and overall size
Frequently asked questions
Why do different bra size calculators give different results?
There's no single universal measuring standard — some sites measure the band above the bust, others below, and formulas vary. This calculator uses the traditional US "round underbust, add 4 or 5" method and states that explicitly.
Is this size guaranteed to fit?
No — it's a starting-point estimate. Breast shape, tissue distribution, and brand-specific fit (sister sizing) all affect real-world fit, and studies suggest most people wear a size different from any single calculator's output. Try the estimated size on and adjust from there.
From the blog
Update history
- 2026-09-02 Launched: bra size calculator using the traditional US band-and-cup formula, with the exact method disclosed on the page. Entirely client-side.