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Bra Size Calculator

Bra size from two measurements, with sister sizes.

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Sister sizes

Same cup volume, different band. If the band feels loose, go down a band and up a cup.

SizeBand fitUKEU

How to measure

  • Band: snugly around the ribcage directly under the bust, tape level and parallel to the floor. Firm but not tight.
  • Bust: across the fullest part, without compressing. Wear a non-padded bra or none at all.
  • Stand normally: not leaning forward, and breathe out before reading the tape.

UK and US cups diverge above D

UK sizing runs D, DD, E, F, FF, G, GG while US sizing runs D, DD/E, DDD/F, G, H. So a UK 34F is roughly a US 34DDD, and the gap widens further up. That is one reason a size that fits in one market may not in another, on top of ordinary brand-to-brand variation.

Your size

—

Across systems

UK—
US—
EU—
AU / NZ—

The measurements

Band size—
Cup difference—

—

Sizing varies between brands — try before you commit

There is no enforced sizing standard, so most people wear two or three different labelled sizes across brands. A calculated size is a starting point for trying things on, not a final answer. If the band rides up at the back, it is too big whatever the label says.

Quick Tool Overview

The Bra Size Calculator finds a band and cup size from two measurements and converts it across UK, US, EU and AU sizing, with sister sizes — the same cup volume on a different band — listed alongside.

What it does
Calculates bra size and converts between sizing systems
You give it
Band and bust measurements in inches or centimetres
You get back
Your size in four systems, plus sister sizes
Best for
Buying online and understanding a poor fit
Calculators Free, unlimited use No sign-up Runs in your browser

About the Bra Size Calculator

Work out a bra size from two measurements — snugly under the bust for the band, and across the fullest part for the cup — with the result converted into UK, US, European and Australian sizing.

Sister sizes are given alongside, and they are the most practically useful part. Cup volume is relative to band size rather than absolute, so a 34C holds roughly the same volume as a 32D and a 36B; if a band feels loose you can go down a band and up a cup and keep the same fit through the cup. Sizing also varies noticeably between brands, so a calculated size is a starting point for trying things on rather than a final answer.

Key features of the Bra Size Calculator

Four sizing systems

UK, US, EU and AU, which diverge above a D cup in ways charts often get wrong.

Sister sizes listed

Go down a band and up a cup to keep the same volume — the most useful fix for a loose band.

Measuring guidance

Where to place the tape and how tight, since technique moves the result by a whole size.

Inches or centimetres

Measure in whichever you have to hand.

Realistic about brands

The page states that sizing varies between labels and a calculated size is a starting point.

How to use the Bra Size Calculator

  1. 1

    Measure the band

    Snugly around the ribcage directly under the bust, tape level and parallel to the floor.

  2. 2

    Measure the bust

    Across the fullest part, without compressing. Wear a non-padded bra.

  3. 3

    Read your size

    Band and cup, converted into UK, US, EU and AU sizing.

  4. 4

    Try the sister sizes

    If the band feels wrong, a sister size keeps the cup volume while changing the band.

Frequently asked questions

Measure snugly under the bust for the band, then across the fullest part of the bust for the cup. The difference between the two determines cup size: one inch is an A, two a B, and so on.

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