Bra Size Calculator

What this calculator does

Bra size is a starting point made from band and cup measurements. This calculator estimates a UK size from underbust and full bust measurements.

Formula used

Underbust is converted to inches and rounded to an even band size. Cup size is estimated from the difference between bust and band measurements.

How to read the result

Fit depends on shape, style and brand. The right size should feel supportive without the band riding up or the cups cutting in.

Assumptions

• Uses UK cup progression.
• Measurements should be taken with a soft tape.
• Sister sizes may fit better depending on the bra style.

Sources and checks

This calculator uses a standard public formula. Where rules or thresholds can change, source links are listed on the relevant page.

Frequently asked questions