A survey conducted by the Bras.co.uk website found that two thirds of women (66%) thought that they were wearing the correct bra size - and yet three quarters (74%) of those same women wrongly believed that a woman wearing a 28DD bra would have the same size breasts as a woman wearing a 34DD.
"It's a mistake that a lot of women make," says Rhona Marshall of Bras.co.uk. "In fact your cup size is relative to your strap size - the cup of a 28DD is smaller than the cup of a 34DD. If you are slim or have a small build, you may need a larger cup size than someone who isn't as slim or who has a bigger frame. It doesn't mean you have bigger breasts than them, only that your cup size is bigger."
How to find your true bra size
To find out your true bra size, firstly measure around your chest, under your bust, where the lowest part of your bra should sit. For this first measurement, the tape measure should be held quite firmly but should not feel uncomfortable. Try to relax - don't try to breathe in - and make sure the tape measure doesn't slip down your back while you take your measurement. Take this measurement in inches and if it is an even number, add four, if it is odd, add five. The resulting number is your band size.
Secondly measure around the fullest part of your bust. The tape measure should sit lightly on your bust but not squash it. This measurement in inches is your bust size and is used to work out your cup size. The cup size is obtained by subtracting the band size from the bust size.
If the two are the same, you are an A cup. If your bust size is one inch larger than your band size, you are a B cup, two inches larger and you are a C cup. Three inches larger a D cup. Four inches larger a DD cup. Five inches larger an E cup. And so on up to a K cup.
What to look for in a well fitting bra
Back strap
Does the back strap ride up?
If the bra strap is riding up at the back, then the back size is too large. The weight of the breasts cannot be supported unless the strap fits snugly around your rib cage.
Most bras have a number of hooks to allow you to adjust the tightness of the back strap. Ideally your new bra should fit perfectly on the loosest setting, allowing you to tighten the strap as the material loses elasticity over time.
A good test when you're trying on a bra is to lift your arms. If the back rides up, try the band size smaller.
Is the back strap digging in?
The back strap should be tight, but if it is uncomfortable around your ribs it is possible the back size is too small.
Try a back size larger or adjust the back strap to its loosest setting.
Shoulder strap
Are the shoulder straps digging in?
The backstrap of a bra provides the majority of support for the breasts. If the back strap is too large, the shoulder straps then have to support more of the weight and this can cause them to dig in.
Try adjusting the back straps. If that doesn't work, a smaller back strap size is recommended.
If you have large breasts, look for wider straps which help to spread the weight load.
Are the shoulder straps slipping?
If the shoulder straps of your bra are slipping, tighten the straps or opt for bra with wider straps.
Front of the bra
Does the front sit flat against your body?
If the centre of the bra at the front is not against the body, it is possible that the cup size is too small.
Is your underwire bra poking you in the chest?
If the underwire in your bra is poking or pinching you in the chest, you should either try going up a cupsize or opt for a softer bra without wire.
Bra Cup
Do your breasts bulge out of the cup?
With a well fitting bra there should be a smooth line where the fabric at the top of the cup meets your bust.
If you are bulging over the top or out the sides of the cups, then the cup size is too small. The "four boobs" effect is not an attractive look with your top off but even worse with it on.
Bulging out over the top of the cup may also be due to the bra style you have chosen. A plunge bra for example will not offer adequate support if your breasts are not as firm as they once were, and the breast tissue may bulge even if you are wearing the correct size.
Is the cup wrinkled?
If there are creases in your bra cups, the cup size is too large.
Is your bustline sagging?
If your breasts are not being supported, firstly check that the back strap is not riding up. If it is try a smaller band size.
If the band is fine, shorten the straps.
For those who are more generously proportioned, avoid stretchy fabrics or choose a firmer support style with rigid straps.
The Perfect Fit
Your bra should be firm, but comfortable. Standing side-on to a mirror, the strap should be horizontal and should never be riding up at the back.
The band should lie flat against your body and follow your shape all the way around your chest without being pushes out by your breasts.
Your bust should fit comfortably within the cups, with no spilling out, pressure or looseness. There should be a smooth line where the fabric at the top of the bra meets your body.
