Bra Size Calculator — Find Your Band and Cup Size
Measure your underbust (snugly around the ribcage below the bust) and your overbust (loosely at the fullest point of the bust), then get your UK/US band size, cup letter, and full bra size instantly.
Measurement unit
in
in
UK/US bra size: 32C
- 1
Round to nearest whole inch
32Underbust measurement rounded to the nearest integer inch. - 2
Band size (nearest even inch ≥ 28)
32Odd results are increased by 1 to give an even band number; minimum band 28.
How does this calculator work?
Measure underbust snugly in inches and round to the nearest even number for the band. Measure overbust loosely and subtract the band: 1 inch difference = A cup, 2 = B, 3 = C, 4 = D, 5 = DD/E. Combine band and cup for your UK/US size — e.g., 32 band + 3 in = 32C.
Formula
How this is calculated
The band size is determined by your underbust — the circumference of your rib cage just below the bust, measured snugly. The modern UK/US method rounds that measurement to the nearest even inch (so 31 rounds to 32, 33 rounds to 34), giving the band number. Older methods added 4 or 5 inches, but most current fit guides use the snug-measurement approach for a more supportive fit.
The cup size reflects how much larger the fullest part of the bust is than the band number. Each inch of difference corresponds to one cup letter: 1 inch above band = A cup, 2 inches = B, 3 = C, 4 = D, 5 = DD/E, and so on. If your overbust equals your band number the result is an AA cup.
Bra sizing is not universal. European (French, Italian, Spanish) systems use centimetre-based band numbers and may map cup letters differently. Cup letters also scale with the band — a 34C and 36C have the same cup volume only in sister-sizing terms. Use this as a starting point and try several brands, as cut, underwire shape, and fabric stretch vary significantly.
Frequently asked questions
Stand straight, wear a non-padded bra or no bra, and use a soft tape measure. Measure underbust directly below the bust as tightly as you can without discomfort. Measure overbust at the fullest point of the bust — usually at nipple level — keeping the tape parallel to the floor but not compressing the tissue.
Brands differ in how they cut fabric, shape underwires, and grade sizes. A 34C from one brand may feel like a 34B or 34D from another. Sister sizing — moving one band up and one cup down (34C → 36B) or vice versa — maintains the same cup volume and can help when you're between sizes.
UK and US sizes share the same band-in-inches and A/B/C/D letters up to D, then diverge: UK uses DD/E, DDD/F, G; some US brands use E, F, G differently. European sizes (e.g., French 90C ≈ UK 36B) use centimetre-based bands — roughly multiply the inch band by 2.54 and round to the nearest 5.
Also known as
TG we-Calculate Editorial Team. (2026). Bra Size Calculator — Find Your Band and Cup Size [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/bra-size-calculator
TG we-Calculate Editorial Team. "Bra Size Calculator — Find Your Band and Cup Size." TG we-Calculate. 2026. https://we-calculate.com/calculator/bra-size-calculator.
TG we-Calculate Editorial Team, "Bra Size Calculator — Find Your Band and Cup Size," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/bra-size-calculator
@misc{wecalculate_bra_size_calculator, title = {Bra Size Calculator — Find Your Band and Cup Size}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/bra-size-calculator}}, year = {2026}, note = {TG we-Calculate} }
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