About

This site is a free, independent bra size calculator and sizing reference. It exists to answer one question well: given two honest measurements, what size labels should you actually try — in any country?

What we do

The calculator converts an underbust and a bust measurement into starting bra sizes for six international systems — US, UK, EU, FR/ES, AU/NZ and JP — together with sister sizes for each. Around it sit measurement guides, per-system size charts, cup-size explainers and a fit troubleshooter, so the number from the calculator can be understood, cross-checked and verified on a real body.

How the sizing data works

Each sizing system is defined by its own data: its band intervals, its cup sequence, its rounding rules and its display format. There is deliberately no single global formula — a UK 32DD and an EU 70E are two labels for the same measurements, reached through each system's own arithmetic. System data is versioned, sourced from published size charts and standards families (including EN 13402-style continental labelling and the JIS L 4006 label family), and can be updated without touching page logic.

Privacy first

Everything runs locally in your browser. Measurements are never uploaded, stored on a server, or sent to analytics. The only thing remembered is an optional session copy of your own inputs, and it disappears when you close the tab.

Honesty policy

Bra sizing is conventions, not physics: brands cut patterns independently, so no calculator can promise an exact size. Every result here is labelled a starting size and paired with fit checks, because an honest starting point beats a confident wrong answer.