Bra Size Calculator & Converter

Bra sizing is one of the more confusing corners of clothing: there's no single global standard, methods disagree even within one country, and the same cup letter means a different volume depending on the band it's paired with. This calculator handles the two things people actually search for — working out a size from measurements, and converting a size you already own into another country's numbering — in one page, with an honest explanation of the method behind each result.

In "measure my size" mode, enter your underbust and bust measurements (inches or centimetres) and the tool applies the traditional band formula — underbust rounded to the nearest inch, plus 4 if that number is even or plus 5 if it's odd — alongside a modern snug-fit estimate, then maps the bust-minus-band difference onto the standard AA, A, B, C, D, DD/E, DDD/F, G, H… cup ladder. In "convert between size systems" mode, type a size like 34B, choose the country you're converting from and to, and the tool applies real published band tables (US/UK count in inches, EU counts in centimetres rounded to 5, France runs 15 cm above the EU number, and Italy uses a simple sequential count) together with a cup-letter equivalence table, since UK letters diverge from US ones above a D cup. Every result also lists its two sister sizes — the same cup volume under a different band-and-cup combination, such as 34B, 36A and 32C all holding roughly the same cup capacity.

None of this replaces trying garments on: sizing methods genuinely vary between brands, fitters and even between different bras from the same label, and this calculator says so plainly with every result — use it as an evidence-based starting point. For sizing the rest of a wardrobe, the site also has a shoe size converter and a clothing size converter covering dresses, shirts, suits and trousers across the same kind of international systems. Everything here runs locally in your browser from static bundled tables: nothing is uploaded, no account is needed, and it keeps working offline once the page has loaded.