📏 Bra Size Calculator

Enter your underbust and bust measurements to estimate your US bra size (band + cup).

Estimated bra size (US)

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Band — Cup — Difference —

⚠️ This result is an estimate based on a standard sizing method. Bra sizes vary significantly by brand, country, and style — try on before buying or get a professional fitting.

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How this calculator works

This calculator uses a widely used US sizing method. The band size is your underbust measurement in inches rounded to the nearest whole number; if odd, 1 is added to make it even. The cup size comes from the difference between your bust measurement (inches) and the band: under 1" = AA, 1" = A, 2" = B, 3" = C, 4" = D, 5" = DD/E, 6" = DDD/F, 7" = G, 8" = H. For example, a 30" underbust with a 34" bust gives band 30 and a 4" difference — 30D. Centimeter inputs are converted internally (1 inch = 2.54 cm).

Tips for accurate measuring

Measure the underbust horizontally, directly below the bust, with the tape snug against the skin but not tight. Measure the bust across the fullest point, keeping the tape level — ideally in a thin shirt or an unpadded bra. Measure after exhaling naturally, and since your body changes with time of day and posture, take two or three measurements and use the average to reduce error.

Frequently asked questions

Can the result differ from the size that actually fits me?

Yes. Sizing methods differ by country and brand (some older methods add 4–5 inches to the underbust), and actual dimensions vary between products with the same label. Treat this result as a starting point and confirm by trying on.

How does this relate to Korean/Japanese sizes (e.g. 70A)?

Korean and Japanese sizing uses the underbust rounded to the nearest 5 cm (65, 70, 75…) as the band, with cups defined by the cm difference to the bust. A US 30 band is roughly a Korean 65–70, but exact mapping varies by brand.

What is a sister size?

Going down one band and up one cup (or vice versa) gives a size with a similar cup volume — e.g. 32C ≈ 30D ≈ 34B. If the calculated size does not fit well, try its sister sizes.