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Bra Size Calculator
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Bra size calculator

Two tape measurements give you the size to try first. Your numbers never leave this page.

Quick uses 2 measurements, detailed uses 6
Units

Measure over a thin, non-padded bra or nothing at all. Drag the tape or type the number.

Around your ribs, right under your bust. Firm, but you can still breathe.

in

Standing, tape level and resting on the skin without squashing.

in

Your starting size

Add both measurements to see it here

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How to work out your bra size by hand

Your band is your snug underbust rounded to the nearest even inch. Your cup is the number of inches your bust measures above that band: 1 is an A, 2 is a B, 3 is a C, 4 is a D, and so on.

Say your underbust is 33¼ inches and your bust is 38 inches. The underbust rounds to a 34 band. The bust is 4 inches above 34, which is a D cup, so you would start with a 34D.

Letters split after D. The same fifth inch is DD in the US and UK, but E in Europe, and the sixth is DDD in the US and E in the UK. Bra cup sizes in order has the full list for each country.

Underbust gives you the band

The band does most of the supporting, so it needs to be firm. Keep the tape level at the back, and check it in a mirror.

Bust gives you the cup

Keep the tape resting on your skin at the fullest point. Breathe out and read it at the front. See the full measuring guide.

Quick or detailed: which should you use?

Quick mode takes two measurements, which is enough for most people. Choose detailed mode if your bust is fuller, your tissue is softer, or quick results have let you down before. It adds a loose and a tight underbust, plus leaning and lying bust readings, because soft tissue measures differently in each position.

What makes this calculator different

  • It uses your real underbust. No adding inches to the band, so you are less likely to end up on a loose band with a cup that is too small.
  • It tells you when you are between sizes. When your numbers sit close to a line, you see the neighbouring size and why it is worth trying.
  • It shows the working. Every result explains how the band and the cup were reached, so you can check it.
  • It catches slips. Enter 85 while set to inches, or swap your two numbers, and you are told before you get a wrong size.

Common questions

How do I calculate my bra size?

Measure snugly around your ribs just under your bust, and round to the nearest even inch. That is your band. Then measure the fullest part of your bust and subtract the band. Each inch of difference is one cup: 1 inch is an A, 2 is a B, 3 is a C, 4 is a D.

How accurate is a bra size calculator?

A calculator gives a reliable starting point, not a final answer. Sizing differs between brands and styles, and a 2012 study in Ergonomics found tape measurements alone tended to overstate band size and understate cup size compared with professional fit criteria. Try the suggested size, then check how it fits using the fit checker.

Should I measure with a bra on?

Measure over a thin, non-padded bra, or nothing at all. Padding and moulded cups add to your bust reading and push the result up a cup or more. For the detailed mode, measuring without a bra gives the most useful readings.

Does this calculator add 4 inches to the band?

No. Adding 4 or 5 inches to your underbust is an older method that tends to give a band that is too loose. This calculator uses your actual snug underbust. How the calculator works explains the choice.

Why do I get a different size from a shop or another calculator?

Shops often fit to the sizes they stock, and older calculators add inches to the band. A different number does not always mean a different fit: 34C, 32D and 36B all share the same cup volume. These are called sister sizes.

What if my two breasts are different sizes?

That is very common. Measure across the fuller side, fit the bra to the larger breast, and use a removable pad or an adjusted strap on the other side if you want them to look more even.

How often should I measure my bra size?

Re-measure whenever your weight changes, during and after pregnancy, when you change your exercise routine, or when your current bras stop feeling right. Your size can also shift a little across your menstrual cycle, so measure at a typical time for you.

Are my measurements saved or sent anywhere?

No. The calculation runs entirely in your browser. Your measurements are never sent to a server, and they are gone when you close the page.

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