Here's how a bra should fit. If you're struggling with any of these pain points, it's time to tackle your lingerie drawer
I've been talking to women about their boobs for 20 years. Here's how your bra should fit, if it doesn't, it's time to fix it

We're all guilty of holding onto those old lingerie, the comfy pieces that have been with us for years, which is fine, as long as the fit is still good. But if you're wondering how a bra should fit, and if you're still servicing your needs, I've asked some lingerie experts to give us the low down, to make sure that your best bras are helping to give you all the support you need.
A recent survey by lingerie specialists, Pour Moi, revealed that 91% of women are wearing the wrong bra size, and if you're not sure, you might be amongst them. Wearing a badly fitting bra not only stops your clothes from sitting correctly, altering your whole silhouette, but it can also cause back and neck aches and the tissues in your bust to stretch, leading to sagging.
If you've never been to a professional bra fitting appointment or investigated how to measure bra size at home, it's time we changed that, and the first port of call is learning how a bra should fit, so you know exactly what you're looking for. "If your bra feels uncomfortable, that’s the biggest red flag," explains Curvy Kate's Bra fitting expert, Katie Weir. "For years, women have been led to believe that discomfort is just part and parcel of wearing a bra, but that’s simply not true. The right bra should feel like support, not restriction".
How a bra should fit, the key things to look out for - and the red flags
“If a bra fits you well, the backband will sit horizontally around your body, which will offer a good level of support,” says Laura Franklin, Customer Services Manager at Bravissimo. “The wires in between your boobs will be flat against your chest, and the wires beneath your arms will sit on your ribcage and all the way round to your underarms.” Wires should never, ever, sit on your breast tissue.
Two of the most common causes of an ill-fitting bra are a backband that’s too big, and a cup that’s too small. Learning how to measure yourself, if you don't have access to professional fitters, and remembering that bra sizing can change throughout your cycle should help you avoid ending up with lingerie that doesn't give you the uplift you need.
How do you know if your bra is too big?
The fit of your bra is dependent on two factors - hence the number and the letter sizing (eg. 34, C). The number corresponds to the back band size, while the letter represents the size of the cup.
For a correctly fitting back band, you should be able to just about run a finger underneath, and the band should sit flat against your back. If the strap is riding up, or is so stretchy you can pull it far off your back. This is the incorrect size, and it is too big.
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The back band should be doing the largest part of the heavy lifting when it comes to how a bra should fit and feel. This is where the biggest and cleverest part of bra engineering kicks in.
Katie explains: "It’s common for people wearing cup sizes that are too small to also be wearing backbands that are too big. One giveaway? Red marks or grooves on your shoulders? This means the straps are carrying all the weight, rather than the backband anchoring the support."
Sound familiar? If your strap is riding up your back, the shoulders are slipping off (and you have adjusted the pulley on the shoulder straps, if you aren't filling the cups, or you're feeling generally unsupported, and without a firm cupping lift, you're bra is most likely too large.
How do you know if your bra is too small?
Thinking you're bra might be on the small side? You've got a whole different set of red flags to look out for.
"If your bra is too small, you’ll likely feel the wires digging painfully into your underarms or breast tissue," Katie shares.
Pinching is one of the most common complaints. In fact, after the Curvy Kate bra quiz, 82% of women found they were wearing the wrong bra size.
"And it’s often the pinching that makes people give up on underwired bras altogether. But the wires aren’t the enemy, the fit is".
If your bra is too small, you will also notice that the cups are filled incorrectly. If you have overspill out of the top, side,s or bottom of the cups, then it's a sign that the bra is too small. And if the back band feels so restrictive that there is bulging around the sides or spilling over the back band, you're bra is too small.
If you find your back area is a particular pain point in terms of getting a smooth finish, once you've nailed sizing, try one of the best bras for back fat, as they often have wider back bands or higher and more supportive backs to help give a contoured and smooth finish.
How can you make your bras fit properly?
The first thing to do is to be honest with yourself. If the above descriptors of bras that are too big or too small resonate, it's time to be ruthless with your lingerie drawer. I know it can feel daunting, but if you have somewhere locally that offers bra fittings, expert advice is the quickest way to finding the best fit and most comfortable bra - trust the experts. Don't feel awkward, I guarantee they have seen it all before, and they just want you to leave feeling supported in every sense of the word.
I promise you, a correctly fitting bra will make all your clothes fit better, you'll stand taller, feel happier in your clothes and there is no reason for your bra to be painful at all.
Remember, though, just as jeans vary in size from shop to shop, not all bra sizes are equal, and not all brands have the same cut, so as with everything, there is trial and error, regular measuring and being aware of the signs of a bad fit, so you can embrace the good ones.
“We recommend fastening a new bra on its loosest hook so that you can tighten it as it stretches over time as you wear and wash it; so if your bra is feeling looser than it first did around your back, try it on a tighter hook,” says Laura. “Sometimes your bra straps can fall down or dig in, and all it takes is a slight adjustment to make them feel more comfortable. It is also worth checking that your boobs are fully enclosed in the cups - we find a scoop, wiggle, and jiggle does the trick.”
How a bra shout fit checklist
Katie put together this speedy checklist for a how a bra should fit:
- The underwires fully encase your breast tissue without digging in.
- The wires sit firmly between the breasts, flat against your skin.
- The backband sits straight and snug, with a firm two-finger tension.
- Shoulder straps are comfortably secure,again with two-finger tension, and the adjusters sit below the top of your shoulder.
- Your breasts are fully contained in the cups with no spillage, bulging, or gaping.
How a bra should fit if you have one boob bigger than the other
The good news is that nearly everyone has one boob that’s bigger than the other - and it’s normally the left. The bad news is that not all bras are designed to cater for these differences.
Katie explains how to cope with this very common issue. "Asymmetry is incredibly common; in fact, most women have some difference between their breasts. For some, it’s subtle; for others, it can be a couple of cup sizes or more.
"To achieve balance and a comfortable fit: Opt for bras with a stretch top cup, which moulds to each breast individually and offers a more custom fit. These are far more effective than padded styles, which often gap or look uneven.
"Adjust your straps individually, tightening the strap slightly on the smaller side can help lift that breast into the cup more evenly.
And my favourite piece of advice if this is a big concern for you:
"If there’s more than a one-cup difference, I highly recommend the brand Evenly," shares Katie. "It's Bra Balancers and Boob Shapers provide natural-looking symmetry and can make a big difference to both shape and confidence".
6 of the bras that woman&home testers really rate
Now you understand how a bra should fit, these are 6 bras that the woman&home team really rate for support, lift and comfort.
One of the best bras for large busts, Curvy Kate is renowned for its uplifting lingerie up to an H cup. With side support to push your bust line forward, this bra gives a lovely rounded shape.
Available in 14 different colourways, this smooth bra is seamless for an invisible finish under clothing. It has smoothing properties too, making it one of the best bras for back fat, even though it is billed as a minimiser bra.
This ribbed design is great for smoothing back fat, as well as just being a comfortable, soft bra. Seamless, stretchy, if you're debating bra vs bralette, try this stylish scalloped design.
Fashion editor, Julie Player slated this style as one of the best bras for mature women. Available up to a J cup and 42 back, it has a great range of sizes too.
A good strapless bra feels like the ultimate unicorn purchase when it comes to how a bra should fit, but as the band of your bra is actually doing all the heavy lifting, going strap-free need not be a challenge. This Pour Moi design made our guide for the best strapless bras.
Lightly padded and gently shaped, our tester, freelance fashion editor, Matilda Stanley, rated this the most comfortable bra. Wire-free, it still gives great shape.
Having a well-fitting bra is an absolute foundation for having good style. While people might not see your undergarments, the correct fit ensures that your clothes sit correctly, with darts and seams falling in the right place. And of course, a good fit means maximum comfort too, wired or not.
If this lowdown has made you realise your lingerie drawer is missing the mark, making great-fitting bras for all occasions should be your next fashion project. For me, this very much falls into the self-care category as the right support will help you stand taller and feel more comfortable, literally and figuratively.
Kate is a freelance contributor to woman&home, covering everything she loves most: fashion, fiction, and fancy face cream. If she’s not working, she’s probably reading, feeding her online shopping addiction, or judging the taste level of celebrity houses (10/10 for Dakota Johnson, 2/10 for Tan France).
She graduated from Central Saint Martins in 2020 with a BA in fashion journalism, and her byline has also appeared in British Vogue, The Times, and Marie Claire.