Bra Sizing Guide Calculator

A well-fitting bra can make a big difference to comfort and support, yet bra sizing can be confusing, with different methods, cup letters and brands that don't quite match. Measuring yourself at home is a good starting point before you shop or book a professional fitting.

This guide explains how UK bra sizes work and how to measure accurately. To turn your measurements into a size, use the bra size calculator.

How UK bra sizes work

A bra size has two parts:

• The band size, a number such as 32 or 36, which relates to the measurement around your ribcage, just under your bust.
• The cup size, a letter such as C or DD, which reflects the difference between your bust and band measurements.

In UK sizing, each inch of difference between your bust and band is roughly one cup size. Cup letters go: AA, A, B, C, D, DD, E, F, FF, G, GG, H, HH, J, JJ, K and beyond. Note that UK sizing uses double letters, such as DD and FF, which other countries handle differently.

How to measure yourself

For the most accurate result, wear a non-padded bra that fits reasonably well, or no bra, and use a soft tape measure.

1. Measure your underbust (band)

Wrap the tape snugly around your ribcage, directly underneath your bust. Keep it level all the way round and breathe out normally. Note the measurement in inches or centimetres.

2. Measure your bust

Wrap the tape loosely around the fullest part of your bust, keeping it level across your back. It should sit flat without squashing.

3. Work out your size

• Band: round your underbust to the nearest whole inch, then to the nearest even number. For example, 31 inches becomes 32.
• Cup: subtract your band size from your bust measurement. Each inch of difference is one cup size.

For example, an underbust of 32 inches and a bust of 36 inches gives a 4-inch difference, which is a D cup: 32D. The bra size calculator does this for you, including centimetre measurements.

Sister sizes

Sister sizes have the same cup volume on a different band. When you go down a band size, go up a cup, and vice versa. For example, the sister sizes of 32D are 30DD and 34C. They're useful if a bra fits well in the cups but the band is too tight or too loose.

Signs your bra fits well

• The band sits level around your body and feels firm on the loosest hook, so you can tighten it as it stretches.
• The cups hold your breast tissue fully, without gaping or spilling over.
• The centre front (the gore) sits flat against your breastbone.
• The straps stay in place without digging in.
• Underwires, if present, sit behind your breast tissue rather than on it.

Common fit problems

Why your size can change

Bra size isn't fixed. It can change with weight changes, pregnancy, breastfeeding, hormonal changes, exercise and age. It's worth re-measuring every year or so, or whenever your bras start to feel uncomfortable.

Different brands, different fits

Sizes can vary between brands and styles, just as with clothes. A plunge bra might fit differently from a full-cup bra in the same size. Use your measured size as a starting point and try a few styles.

Sports bras

During exercise, especially high-impact activities like running, a supportive sports bra can reduce movement and discomfort. Many sports bras use the same sizing, while some use small, medium and large sizes.

When to get a professional fitting

A professional fitting can be helpful if you're between sizes, find it hard to get a comfortable fit, are pregnant or breastfeeding, or have had breast surgery. Many department stores and lingerie shops offer free fittings.

If you notice any changes in your breasts, such as a lump, a change in shape or skin texture, or nipple discharge, see your GP. Persistent breast pain can sometimes be eased with a better-fitting, supportive bra, as the NHS notes.

Caring for your bras

Looking after your bras helps them keep their shape and support for longer. Hand washing or using a laundry bag on a gentle cycle protects the fabric and wires, and fastening the hooks before washing stops them snagging. Air drying is gentler than a tumble dryer, which can weaken elastic. Rotating between a few bras, rather than wearing the same one every day, also gives the elastic time to recover.