Bra Size Calculator: Fitting

Most women wear the wrong bra size, and it is almost never their fault: the old "underbust plus four inches" formula was never accurate, and every brand bends its own size chart.

Bra Size Calculator works like a tailor instead. You take five measurements with a soft tape, and the app drafts your real bra size from them: band size, cup size, and the reason your current bra never sat right. No camera, no photos, no guessing.

How the calculation works
Your band size comes from your snug underbust measurement. Your cup size comes from the difference between bust and band: one inch of difference is one cup step. It is the five-measurement ABTF method used by bra fitting communities, and the result is deterministic, so the same measurements always give the same size.

What is inside
• A bra size calculator built on the 5-measurement ABTF method, not the outdated +4 formula
• A step-by-step bra measurement guide: what to measure, where to hold the tape and how snug it should be
• Your band size and cup size in one clear result, with a plain explanation of why your current bra digs in, gapes or rides up
• Sister sizes above and below, so you still have options when your size is out of stock
• US, UK and EU size conversion: switch the system and the result recalculates instantly
• Centimetres or inches, and your choice is remembered
• Extra fitting guides on breast shapes and how sizing differs between brands, unlockable inside the app

Who it is for
For anyone who has walked out of a fitting room unsure, ordered one style in three sizes, or decided that straps digging into your shoulders is just normal. Useful before shopping, after a change in weight, during pregnancy and postpartum, and any time a bra that used to fit suddenly does not. Measure once, keep the result, recalculate when your body changes.

Privacy
No camera and no photos, ever. No account, no sign-up, no cloud. Your five measurements and your result stay on your device, the calculator works fully offline, and you can erase everything from Settings with one tap.

Get the tape, take five measurements and see your true fit. Measured, not guessed.