Believe it or not, almost 95% of women wear an incorrectly sized bra! Here’s some advice from BioBust on how bra sizing works, and how to make sure you’re wearing the right size and shape for YOU …

So 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 is made for a smaller frame. A 28F is actually five cup sizes smaller than a 38F, so it is not as big as it sounds! If you are fairly slim, then you may well need a large cup size even though your bust does not 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 kilos is very likely to have an effect on your bra size but it is not often considered even when other clothing is resized.

How to 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, then you should try out bras in both the size below your measurement and the size above. For example, if you measured 31 inches (78,7cm), your band size could be 30 or 32. In most cases, it is 30. If you are EVER unsure, lean towards being too small in the back and too large in the cups.

If your measurement is already an even number, this is your band size. (The exception is if you are extremely underweight or overweight.)

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.

Determine your cup size

Since everyone’s breasts are different in terms of shape, 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 34D bra, and you measure 28 inches, you should probably wear a 28F.

Cup sizes are as follows: AA, A, B, C, D, DD, E, F, FF, G, GG, H, HH, J, JJ, K, KK, L, LL.

Do NOT buy bras from a website with any other cup sizing method!

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 push-up bras.

Check around the cups for any bulging, not only at the front but also at the sides under your arms (and your back!).

Try on a bra with the band and cup size you have 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 breasts fall into the cups.

Fasten the bra on the largest set of hooks and eyes. Don’t worry if it is tricky to fasten, if you are 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 are settled comfortably into the cups.

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

You might 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.

TIPS from BioBust:

Cup sizes above D tend to vary significantly between manufacturers. A well-fitted bra should provide 90 percent of the support from the band, not the straps.

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

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.