Believe it or not, at least 80% of women wear the wrong size bra, some studies show as much as 95%. The most common mistake is wearing a band size which is too big, and/or a cup size which is too small. Although the average bra size is often quoted as 36C, most people who wear this size should actually be wearing either a 34D, 34DD, 32DD or 32E bra. The true average bra size is around 34DD. 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 2 cup sizes smaller than a 38D. 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. 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 different stages of your life. Losing or gaining just a few pounds is likely to have an effect. 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.
How To Measure 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. 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.) For instance, if you measured 31 inches, your band size should be 32. If you measured 34 inches, your band size may be 34 or 36. Many bra fitting guides and calculators will tell you to add four or five inches to your underbust measurement, but this is not correct. The old method was devised by Warners in the 1930s when bra design was in its infancy and does not work with modern, elasticated bras.
2. Determine your cup size. 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. Instead, you must increase the cups by one size for every band that you go down. For example, if you are currently wearing a 34C bra and your underbust measures 31 inches, then you will most likely need a 32D. On a 30" band, this would be a 30DD etc.
In UK sizing, cup sizes are as follows: AA, A, B, C, D, DD, E, F, FF, G, GG, H, HH, J, JJ, K.
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.
4. 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 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, even 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 is the biggest you can completely fill out with no wrinkling of the fabric or space in the cups. You should fill out the cups, but not bulge out anywhere, even in low cut or pushup bras.
* Check around the cups for any bulging, not only along the top edges but also at the sides under your arms.
* Make sure the underwire encloses your whole breast and lies flat against your rib cage.
* If the cups are too big, go down a cup size.
* If they are too small, or even if they seem to fit ok, try on a bigger cup size as well to double check. It's a lot easier to tell if they are too big than too small.
* This measurement applies to the UK, but it can be translated into bra sizes for other countries using an international bra size converter.
* 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 increments - whether the next size up from F is FF or G makes no difference to the size of the bra. Double letters are not half sizes.
* 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.
* 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, distribution of body fat, 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 underbust 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.
* 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!