How to Measure Bra Size


How do bra sizes work? Most people know that bra sizes are made up of two parts - a number and a letter. The number is known as the "band size" or "back size," and the letter is the "cup size." However, what many people do not realise is that cup sizes are in proportion 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 5 cup sizes smaller than a 38F, so it's not as big as it sounds! If you are fairly slim, then you may well need a large cup size even though your bust doesn't look any bigger than average. Larger women may still need a small band size because this relates to the size of your ribcage only - you can still be curvy everywhere else!

Losing or gaining just a few pounds is likely to have an effect on your bra size. Sometimes you go for so long wearing a certain 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.



1. 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.

If this measurement is an odd number, round up to the nearest even number. This should be your band size. For example, if you measured 31 inches, your band size should be 32.

If your measurement is already an even number, you may find that this is your band size, or you may have to go up to the next size (i.e, you may have to add 2 inches.) If you measured 34 inches, your band size may be 34 or 36.

Some bra fitting guides and calculators will tell you to add four or five inches to your underbust measurement, but this is outdated. The "add four" method was popularised by Warners in the 1930s when bra design was in its infancy and does not work with modern bras.

2. Determine your cup size

Since everyone's breasts are different, the most accurate way to determine your cup size is by using your current bra size as a starting point. The cups are sized relative to the band, so if you were to try a smaller band size but keep the same cup size, the cups would be too small.

For every band size you have dropped, you will need to increase the cups by one size. For example, if you are currently wearing a 34C bra and your underbust measures 31 inches, then you will most likely need a 32D.

 - Please refer to Bra Size Conversion Chart


3. Try on a bra with the band and cup size you've arrived at in these steps.

You should not regard this as your definitive size until you have tried on a few bras, and even then you will often find you need a different size in different brands or styles of bra.

After taking the bra off its hanger the shoulder straps will need to be lengthened. Put your arms through them and lean forward slightly so that your bust falls into the cups.

Fasten the bra on the largest set of hooks and eyes. Don't worry if it's tricky to fasten, if you're trying a smaller back size you will notice that you need to stretch it around you to make the hooks and eyes meet.

Still leaning forward, take hold of the underwires and give them a wiggle from side to side to make sure you're settled comfortably into the cups.

For each side in turn, slip your hand into the side of the cup and lift each breast towards the centre.

You will probably have to adjust the length of the shoulder straps. Slip them off your shoulders and adjust the sliders so that the straps are short enough to stay in place but don't cut in.


4. Check the band size

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

You should be able to run your fingers around the inside of the band, but not much more. A good rule of thumb is that you should be able to fit no more than a fist under the back of the bra.

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 so that you can tighten the band as the elastic starts to wear out.

If the band is roomy enough for you to be able to comfortably fasten it on the tightest adjustment, try a smaller band, for example if a 32D is too loose, try a 30DD. Remember that the cup size has to be changed when you move to a different band size - for every band you go down, you must go up by one cup size in order for the cups to remain the same capacity 
and vice versa.

If you can only just fasten the bra and the band is painfully tight on the biggest adjustment, then go up a band size, for example if a 32D is too tight, try a 34C.


5. Check the cup size

The correct cup size should be completely filled out with no wrinkling of the fabric or space in 
the cups, but any spillage means the cup size is too small, even in low cut or pushup bras.

Check around the cups for any bulging, not only at the front but also at the sides under your arms.

Make sure the underwire encloses your whole breast and lies flat against your rib cage.

Check at the sides under your arms to make sure the underwires are sitting on your ribs, not on soft breast tissue. If they're cutting into the sides of your breasts then you need a larger cup size.

If the underwires are pressing painfully against your breastbone at the centre front you may need a smaller cup size or you could try a plunge style with a lower centre front (This is more likely to be a cup size issue than a band size issue.)

If you think the cups might be too small but you're not sure, try on a bigger cup size as well to double check. It will usually be obvious if the smaller size fits better.


6. See how it looks with your top on

You've found a new bra that fits well, maybe in a different size or style to the ones you're used to. Now it's time to see what it does for your figure! If you're trying a t-shirt bra it's also important to make sure it gives you a smooth line under fitted clothes.

If you look side on to the mirror, you should be able to see that your bust is approximately halfway between your elbow and your shoulder.

In a well fitting bra, your bustline will be supported at the right level. A lot of people find that their clothes fit a lot better, and they discover a waist that could never be seen before! If your bustline had previously been quite low because of a poorly supporting bra, you may even find that you need to wear a smaller dress size.

A fitted t-shirt will show up any bulges from cups which are too small, and likewise a moulded bra that is not filled out will show lines at the bust where the edge of the cups are visible. It's also useful to make sure that the colour of your bra is not showing through a thin or light coloured top - if you need to make your bra invisible, go for seamless cups which match your own skin colour rather than the colour of your top.

It is a common concearn that wearing a smaller band size will make a big bulge around your back. However, these bulges are actually caused by the back of the bra riding up when it is too large. You should find that when the band sits lower at the back, it fits firmly and remains horizontal, rather than pushing upwards creating a bulge.



 Cup sizes above D tend to vary significantly between manufacturers. Some brands go to the next letter of the alphabet for each cup size, while others include double letters or miss out certain letters altogether. However, all cup sizes have the same incriments so if DD is skipped, an E will be equivalent - double letters are not half sizes.

A well-fitted bra should provide 80% of the support from the band, not the straps.

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

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.

If you want your bras to last and keep their fit, never wear the same bra two days in a row, even if it has been washed. You should have at least three bras which you can wash and wear in rotation, allowing the elastic to fully recover before it is put under stress again.



 This is only to give you a rough idea of what size to try on first - the fit is more important than the number on the tape measure. Because women are all different shapes, two women with the same measurements will often need a very different bra size.

Do not expect to need the same size in every style of bra, or to able to buy any bra in your "true size" without having to try it on. Different styles will suit different breast shapes, so two women who wear the same size in one bra might need different sizes in another bra.

Ignore anyone who tries to tell your definative size from your measurements alone - especially if they tell you to add several inches to your underbust measurement. Just like dress sizes, bra sizing has changed over the years, and the old method does not work for modern bras.

Don't be tempted to buy the wrong size or a poorer quality bra because it's cheaper. With bras you generally get what you pay for. It's better to have one bra that fits really well, than three that are uncomfortable!