Bra Size Converter

How to use

1. 1Choose the system you already know from the dropdown (US, UK, EU, FR, IT, AU, or JP), or pick Body measurements to size from your underbust and bust.
2. 2For a region size, select your band and cup. The equivalents panel lists the band and cup in every other region instantly.
3. 3For measurements, pick inches or centimeters, then enter your snug underbust (around the rib cage) and your bust (around the fullest part).
4. 4Read the equivalent sizes for every region, and check the sister sizes panel for the same cup volume on a tighter or looser band.
5. 5Use Copy summary to save the full conversion, and scan the band and cup reference charts below for the whole scale.
6. 6Treat the result as a starting point: prefer a brand's own size guide when offered, and try the size on for the best fit.

About this tool

Bra Size Converter translates a bra size between the regional systems you actually meet on product pages, and works out a size from your own measurements, all in your browser. Bra sizing has two independent parts, and conflating them is the cause of most confusion. The band number encodes the rib-cage circumference under the bust, and the cup letter encodes how far the bust projects beyond that rib cage, which is the bust measurement minus the band measurement. The systems disagree on how each part is written. US and UK band numbers are even inches (28, 30, 32, 34 and up) and are identical to each other. EU and Japanese bands are the snug underbust in centimeters rounded to the nearest five (60, 65, 70, 75), French, Belgian, and Spanish bands are the EU band plus fifteen (so EU 75 is FR 90), Italian sizing uses a short ordinal scale (band 1 through 7), and Australian and New Zealand bands are the even numeric bands offset by twenty (a US 32 band is an AU 12). The cup letter is where the real divergence sits: the US ladder doubles letters and has no single E, running A, B, C, D, DD, DDD before continuing to G and H, while the UK and Australian ladder runs A, B, C, D, DD, E, F, FF, G, and the continental EU, French, and Japanese ladder steps straight through A, B, C, D, E, F without doubling. The practical upshot, which this tool makes explicit, is that a US DDD is a UK F and an EU F even though the band number is the same. Pick the system you already know, choose your band and cup, and every other region updates at once, with a copy-summary button for the full set. Switch to the measurements mode to enter your underbust and bust in inches or centimeters: the tool rounds the underbust to a band using the modern even-number method and converts the bust-band difference to a cup at roughly one inch (about 2.5 cm) per cup step, then shows every regional label. It also calculates sister sizes, the pairs that share the same cup volume while moving the band one step (up a band and down a cup letter, or the reverse), which is the standard fix when the band fits poorly but the cup is right. Reference charts for both the band and the cup are included so you can scan the whole scale. One honest caveat runs through the tool: cup volume changes with the band, and lingerie brands cut differently by style, so these conversions are a dependable starting point rather than a guarantee of fit for any single brand. When a retailer publishes its own size guide, prefer it, and try the size on when you can. Everything runs locally in your browser; the measurements and sizes you enter are never uploaded or sent anywhere.

Free to use. Works in your browser. No signup, no login.