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How to measure bra size

Many women are surprised to learn that they’ve been wearing the wrong bra size. There are lots of reasons why women wear the wrong bra size – poor measuring skills, changes in body size, and changes in wardrobe all lead to bra faux pas.

Believe it or not, 80% of women wear the wrong size bra. The most common mistake is wearing a band size which is too big, and/or a cup size which is too small. You may have heard that 36C is the “average bra size”. Although the average bra size is often quoted as 36C, most people who wear this size should actually be wearing a 34D or 34DD bra. Cup sizes are relative to the band size, so a D cup, for example, is not the same size in every bra. A 32D is the same size as a 34C or 36B, but on a smaller frame. A 28F is actually 2 cup sizes smaller than a 38D. You may not think of yourself as being busty, but in moving to a smaller band size you will find that you need a bigger cup size.

Your bra size changes as your weight fluctuates throughout the seasons and the years. Sometimes you go for so long wearing a specific size that you don’t realize it doesn’t fit well anymore and you stop noticing the discomfort. If you’re looking for a better fit, here’s how to find your true bra size.

Important note – the measurements used in the steps of this guide refer to UK bra sizing. Although US bras are theoretically sized according to the same system, there is considerable variation between brands, so if you are in the US you may find you need a bigger band size and/or a smaller cup size than that indicated here. For example, A UK 32E may be equivalent to a US 34DD or even 36D.

Bra size


1. Wear your best supporting bra. The bra doesn’t have to fit perfectly. The objective is to get your breasts to the position that the ideal bra would support, with the weight suspended comfortably. This step is optional, however, so if you can’t find a bra with good support, continue with the measurements.

2. Measure your band size. Run a tape measure all the way around your body just underneath your breasts and take a measurement in inches. Make sure the tape measure is horizontal and fairly snug. Your arms should be down. Round to the nearest even number. This should be your band size. For instance, if you measured 31 inches, your band size should be 32. If you measured 34.5 inches, your band size should be 34.
Many bra fitting guides will tell you to add four or five inches to your under-bust measurement, but this is not correct. The old method was devised in the 1930s when bra design was in its infancy and does not work with modern bras.

3. Measure your bust size. Measure loosely around the fullest part of your bust in inches (not too tightly or the measurement will be inaccurate). If you don’t have a bra, or if the one you have is very poorly fitting, bend over so your back is parallel to the floor and measure around your chest, over your nipples. Round this measurement up to the nearest whole number.

4. Calculate your cup size. Subtract the band size measurement from the bust measurement and determine your cup size as follows: (The cup size calculation may be less accurate for larger cup sizes.)

  Difference in inches  Difference in cm    Cup size
less than 1 inch 1.3 cm AA cup
1 inch 2.6 cm A cup
2 inches 5.1 cm B cup
3 inches 7.6 cm C cup
4 inches 10.2 cm D cup
5 inches 12.7 cm DD cup
6 inches 15.2 cm E cup (US DDD)
7 inches 17.8 cm F cup (US DDDD)
8 inches 20.3 cm FF cup
9 inches 22.9 cm G cup
10 inches 25.4 cm H cup

5. Try on a bra with the band size and cup size you’ve arrived at in these steps. Because there can be wide variations in how bras are manufactured as well as differences between different styles of bras, this size should be starting point.

6. Check the band size. The correct band size is the smallest you can comfortably wear. It needs to be tight enough that the bra is still fairly supportive without weighing down on the straps.

  • You should be able to run your fingers around the inside of the band, but not much more.
  • It should fit on the biggest adjustment, but will probably be too tight if you try to fasten it on the smallest size. Bras are designed to fit like this to leave room for the bra to stretch after you’ve worn it a few times.
  • If the band is painfully tight, even on the biggest adjustment, then go up a band size (and down a cup size to compensate). For example, if a 32D is too tight, try a 34C.
  • If the band is loose enough for you to be able to comfortably fasten it on the tightest adjustment, try a smaller band (e.g. 32D -> 30DD).

7. Check the cup size. The correct cup size is the biggest you can completely fill out. You should fill out the cups, but not bulge out anywhere.

  • Check both the top of the bra and the sides for bulging.
  • Make sure the under wire encloses your whole breast and is flush against your rib cage.
  • If the cup size is too big, go down a size.
  • If it is too small, or even if it seems to fit, try on a bigger cup size as well to double check.
Useful to know:

1inch = 2.54cm

cm x 0.39 = inch

inch x 2.54 = cm


This measurement applies to the UK, but it can be translated into bra sizes for other countries using an international bra size calculator. US sizing may vary slightly – you may find that you need a bigger band size and/or a smaller cup size in US brands.

Cup sizes above D tend to vary much less reliably between manufacturers. Some brands go to the next letter of the alphabet for every added inch, while other brands may simply add on the same letter for every inch.

A well-fitted bra should provide support from the band, not the straps. You should be able to take off the straps and still feel supported by the bra.

Always try on a bra before you buy, and keep an open mind about your size.

It is possible to find out your bra size without a tape measure. If you already wear a bra which seems to fit well in the cup, but is roomy around the band, you can go down a band size and up a cup size until you get to a size you can only just fasten – this is the right size. (e.g. 36C -> 34D -> 32DD)

If you have uneven cup sizes, go with the bigger side. You can support the smaller breast by making that shoulder strap slightly shorter, or alternatively you can pad out the cup.

HOW TO MEASURE BRA SIZE – important to know

As mentioned above, this is only to give you an approximate idea of what size to try on first. Women come in all shapes and sizes, and bra size can be affected by back proportions, breast shape, pectoral muscle mass, and so on. All of these factors can interact to affect your bra size in ways that are impossible to predict.

Ignore anyone who claims to be able to tell you your size with certainty from your measurements – especially if they tell you to add several inches to your under-bust measurement. Just like dress sizes, bra sizing has changed over the years, and the old method does not work for modern bras.

If you have previously been told your size, but now find that a different size fits better, just wear the size that fits! The fit is more important than the number on the tape measure.

(information from HubPages – //

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