How to Measure Your Bra Size

Up to 70% of women are wearing the wrong bra size – unfortunately a lack of retailer training and a misunderstanding of what cup sizes and band sizes stand for means that many women are told the wrong information or just don’t realise that they could have a much more comfortable and supportive bra.

There are two main says to measure your bra size – one is with a measuring tape, and the other is by ‘eyeballing’ your bra to see whether you need to go up or down in your band and your cup measurements. You really need to use both together since sizing differs between brands so you will need to check whether that brand runs ‘true to size’ and really fits you as it should.

Measuring with a Tape Measure

There are two main measurements you need to take – one from your rib-cage underneath your boobs (not including any breast tissue in this measurement) and one around the widest part of your boobs to see what your cup size is.

Don’t squeeze the measuring tape around you – it should just be a loose fit to see how many inches you are around your ribs and the widest part of your breasts.

Your ribs measurement will determine your band size. If you’re an odd number, you will need to round to the nearest even number. How you do that really depends on which is closest – if you are 29.5 inches it makes sense to go for a 30 band, but if you are just under 29 you may want to go for a 28 band and use the last row of hooks when closing.

Once you have your back measurement, it’s time to find your cup measurement – take your bust measurement (across the widest part) and subtract your back measurement. The result determines your cup size and goes up in 1-inch intervals – 1 is an A cup, 2 is a B cup, 3 is a C cup, 4 is a D cup, etc. Double letter cups (like DD) still go up in 1-inch intervals, not 0.5, but an AA cup is a difference of 0.5 inches.

A lot of women are surprised by their bust size, since many people think that a DD cup is meant to look huge. This is probably a combination of factors – a lot of people do wear the wrong size so you may have seen a G cup with huge cleavage crammed into a DD cup. We also see a lot of images of very slim models, and a DD cup on their frame looks a lot different to a DD cup on a size 12-14 woman, which also affects how we view the size. If you’d like a realistic representation of what your size looks like, the Bra Band Project has a lot user-submitted images that you can sort through.

Now that you have your correct bra size, it’s time to try on some bras and see what works best for you.

Shape is as Important as Size

One of the things rarely mentioned in magazines and in shops is that your shape is as important as your size when it comes to finding a bra that feels comfortable and looks great. To figure out your shape, you need to look at a few different aspects of your boobs, including the fullness at the top and bottom, projection (how much they stick out), and the difference between the root and the breast itself.

One of the best graphics I’ve seen to explain different shapes is from A Bra That Fits on Reddit: a fantastic community of (mostly) women who help each other find bras that fit properly.

breast shape guide

Two women could have the exact same bra size, but if one is fuller on the top than the bottom and the other has even breasts or is more full on the bottom, bras will fit differently. The best way to find the right fit is to experiment with different types of bras.

The final factor when it comes to how your bra fits is whether you have shallow breasts or whether they’re projected. The simplest way to see is to look down and decide whether your breast tissue is quite evenly distributed across your chest (which is an indicator that you have shallow breasts) whereas projected breasts are narrower but stick out from your chest more. If your boobs take up most of your chest and start quite close together, it is likely that they’re shallow.

Checking if Your Bra Fits

Bras are no different to other types of clothing – jeans might fit you perfectly in a 10 in one shop, but a 14 is snug in another. Different types of bras fit differently too, so you probably have a different size in balconette bras and plunge bras, depending on your breast shape.

When you’re trying on your bra, check that:

  • The cups don’t wrinkle – if it does, go down a cup size
  • The cups don’t gape – if they do, go down a cup size or try a different style of bra
  • You’re not spilling over your cups – if you are, go up a cup size
  • The underwire isn’t on your breast tissue – if it is, try a larger cup or larger band
  • The underwire doesn’t poke into your armpit or sit far back on your ribcage – if it does, try a smaller band
  • The band doesn’t cut into you – if it does, try a larger band
  • The band can’t fit a fist underneath – if you can, try a smaller band
  • The middle of the bra isn’t sitting on your boobs – it should be on your sternum – if it does, try a larger cup size and smaller band size
  • The straps don’t cut into your shoulders – if they do, try a smaller band size (the band should be proving most of your support)
  • The straps don’t fall down off your shoulders – if they still feel loose when you’ve tightened them, try a smaller band size and larger cup size

Your bra should be snug around you, but not painful, and offer support without digging into you anywhere. Your boobs should sit comfortably in the cups without spilling out over the tops of sides. Check out my page on how to try on a bra to roadtest it a little bit and make sure you’ll be comfortable wearing it all day.

Different Bra Types Fit Differently

You probably have a few different bra types, including sports bras, balconettes, push up bras, and plunge bras. These all fit and contain your boobs differently, which can mean that your size varies. I’m a 34F in balconette bras, but a 34GG in plunge bras so there can be quite a bit of variation.

Once you have your bra size, try on a variety of different bras to see what works for you. If you’re shopping in person, go to a department store so that you can try on different brands too since sizing varies. Trying on some plunges, some balconettes, and some full-cup bras in different brands will speed up the process of finding your perfect bra.

Apply the list above each time you try on a bra, and check out the troubleshooting guide to see whether you need to go up or down a size if you the bra doesn’t quite fit properly.