How accurate is this UK bra size calculator?

Our calculator uses the modern UK sizing method — measuring underbust directly for band size and the difference between bust and band for cup size. This is the standard used by leading UK lingerie brands including Bravissimo and M&S. However, fit varies between brands, so we always recommend trying before buying.

What is the difference between UK and US bra sizing?

UK and US band sizes are numerically identical. Cup naming diverges from D onwards — UK 'DD' equals US 'E', UK 'E' equals US 'DDD/F'. Our calculator shows your US equivalent automatically.

What are sister sizes in bra sizing?

Sister sizes have the same cup volume with adjacent band and cup combinations. For example, 34D, 36C, and 32E all contain the same volume of breast tissue. If a brand doesn't carry your exact size, a sister size is the closest equivalent.

Should I measure with or without a bra on?

Measure without a bra, or wearing an unpadded bralette. Padded bras add extra volume which skews the cup measurement. Stand upright, breathe normally, and keep the tape parallel to the floor throughout.

When should I re-measure my bra size?

Re-measure every 6–12 months, or after any significant weight change, pregnancy, breastfeeding, or hormonal change. Bra size can shift more than most people realise — even a few kilograms can change both the band and cup.

Why does my bra size differ between brands?

Every brand cuts bras differently — cups may run small or large, and band stretch varies. Use your calculated size as a starting point and adjust by ±1 cup or band as needed when shopping new brands.

✦ Bra Size Blog

Tips, Guides & Sizing Advice

Expert articles on how to measure your bra size UK, find the perfect fit, understand sister sizes, and convert between international sizing systems.

Sizing Guide How to Measure Your Bra Size at Home — The Complete UK Guide

Step-by-step NHS-recommended instructions for getting an accurate bra size measurement at home. All you need is a soft tape measure and five minutes.

2 May 2026 6 min read Read →

Fit Tips Signs Your Bra Does Not Fit — and Exactly How to Fix Each Problem

From a riding band to wrinkling cups, learn how to spot every common fit problem and which exact size adjustment solves it.

28 Apr 2026 7 min read Read →

Sister Sizes What Are Sister Sizes? How to Find Yours and Use Them

Sister sizes share the same cup volume with a different band. Here is how to find yours and when to use them when shopping across UK brands.

20 Apr 2026 5 min read Read →

International Sizing UK vs US vs EU Bra Sizes — The Complete Conversion Guide

UK and US sizes diverge from DD onwards. This guide covers every conversion for US, EU, France, and Australia with practical tables.

14 Apr 2026 6 min read Read →

Bra Care How Often Should You Replace Your Bra? Signs It Is Time to Let Go

Most bras last 6–12 months with regular wear. Learn the warning signs that yours has passed its best and how to extend its life.

7 Apr 2026 5 min read Read →

First Bra First Bra Size Calculator UK — A Complete Guide for Teens and Parents

Finding the right first bra size can feel daunting. This friendly guide walks through how to measure, what types to buy, and how to make it a positive experience.

1 Apr 2026 7 min read Read →

Ready to Find Your Perfect Fit?

Use our free UK bra size calculator — accurate, easy, and NHS-standard.

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