How to Buy a Bra That Fits

Wearing the right-size bra is important whatever your bust size. An ill-fitting bra can cause back and neck pain and poor posture, not to mention painful rubbing and chafing. Giving your breasts the right support is not only vital for comfort, but for general wellbeing, too, so regular fittings are important.

We recommend getting fitted every six to twelve months, as your breasts can fluctuate in size thanks to hormonal changes during puberty, pregnancy, or the menopause, and also after weight loss or gain. Our in-store and online Bra Fit service has instant appointments available, or you can use the booking system to choose a more convenient time.

Whatever your bra size, the right fit still matters for comfort and long‑term support. Choose styles that complement your shape – we offer a wider variety of bras to help you find the perfect fit for you.

If you have a smaller bust, you might think you don't need quite as much support as those who wear an E-cup or above, but getting the fit right is just as important – not only for comfort, but to prevent any premature sagging. Choose a bra style designed to flatter your shape. “For women with smaller busts, we have a range of bralettes, crop tops, non-wired and wired bras, in cup sizes A to E, so every customer will find a style to suit,” says M&S bra technologist Stephanie Dear.

The tell-tale signs that your bra is too big or small:

Spilling out over the cups: Choose a larger cup size. If you're spilling out at the front and under the arms, you might need to go up a cup size.

Straps digging in: Support should come from your bra's underband, not the straps. Loosen the straps and then see if the underband feels too loose or too tight.

Your breast escapes from the bottom of the cup: You need a bigger cup size and possibly a smaller underband.

Uncomfortable front underwiring: Wiring should always sit flat between your boobs, if it doesn't, you need to increase your cup size.

Bra rising up at the back: If the bra is less than a year old, you need a smaller back size. If it's older, the elastic might have gone, so it needs replacing.

Wiring digging in at the side: You need a bigger cup size and a smaller underband size.