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How to measure your bra size

You need two measurements: a snug one around your ribs under your bust, and a relaxed one around the fullest part of your bust. The first, rounded to an even inch, is your band. The difference between them gives your cup.

All you need is a soft tape and a mirror. Take off any padded bra first. A thin, unlined bra is fine, or wear nothing at all.

  1. 1. Measure your underbust

    Stand straight and wrap the tape around your ribs, right where your bust meets your body. Keep it level and snug, and breathe out as you read it. It should feel firm, like a band that is holding on, without stopping you from breathing.

  2. 2. Round to your band

    Bands come in even numbers, so round to the nearest one. A reading from 31 up to just under 33 inches is a 32 band, and exactly 33 goes up to 34. In centimetres, divide by 2.54 first.

  3. 3. Measure your bust

    Measure the fullest part of your bust with the tape level. It should rest on your skin without pressing in. Stand with your arms relaxed by your sides as you read it, because raised arms lift your bust and change the number.

  4. 4. Work out your cup

    Subtract your band from your bust and count one letter for each inch. With a 34 band and a 38 inch bust, the difference is 4 inches, so you are a 34D.

    Prefer not to count? The bra size calculator does this for you and converts the result for your country.

Fuller or softer bust? Take two more readings

Soft tissue can settle differently depending on how you are standing, so one upright reading can undersell your cup. Two extra readings help.

Leaning. Bend at the hips to 90 degrees with your back flat, and let your bust hang.
Lying. Lie flat on your back and take the tape over the fullest part of your bust.

Mistakes that give you the wrong size

Measuring over a padded bra
Padding adds to your bust reading and can move you up a cup or more.
Letting the tape drop at the back
A tape that slopes gives a longer reading. Check it in a mirror.
Adding inches to your band
Older guides say to add 4 or 5 inches. That tends to give a band too loose to support you.
Pulling the bust tape tight
Squashing your bust reduces the reading and points you to a smaller cup than you need.
Measuring once
Take each reading twice. If they differ, use the middle value.

Measuring is only the start

A tape cannot see the shape of your breasts or feel how a particular band sits. In a study published in Ergonomics in 2012, researchers compared the traditional tape method with professional fitting criteria in 45 women. The tape tended to overstate band size and understate cup size, and more so on larger bands.

So take your measured size to a fitting room, or order two sizes, and judge it on your body. The bra fit checker tells you what to try next if something feels off.

Measuring questions

How do I measure my bra size without a tape measure?

Use a piece of non-stretch string or ribbon. Wrap it where the tape would go, mark or pinch where it meets, then lay it flat against a ruler. Take each reading twice, as string is easier to pull too tight.

Do I measure my bust standing or lying down?

Standing is enough for most people. If your bust is fuller or softer, add a reading leaning forward and another lying on your back. The detailed mode in the calculator averages all three.

What time of month should I measure?

Pick a time when your breasts feel typical for you, as many people find they feel fuller or more tender before a period. If your size changes noticeably, it can help to have bras in both sizes.

Can I measure my bra size by myself?

Yes. A mirror is all you need to check that the tape is level across your back. If you find the back hard to judge, hook the tape over a door handle or ask someone you trust to check it.

What if my measurement falls between two numbers?

Round to the nearest even number for your band, and try the neighbouring size as well. The calculator shows that neighbour automatically when you sit close to the line.

Does this method work if I am pregnant or nursing?

The method is the same, but your size can change quickly during pregnancy and nursing, so re-measure often. Many people prefer flexible styles at this time, and a specialist fitter can help.

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