Sorry, we should be measuring our bra size how often?! Yep, that's right, according to Boux Avenue's bra fitting experts, the brand recommends you get your bra size measured “ideally every six months.” But in theory, you should be measuring your bra size every time you go to purchase new underwear. Given that wearing the wrong bra can cause back pain and plain old discomfort, not to mention result in your boobs looking far from their best (sorry, but droopy and saggy ain't chic), it really is worth prioritising.
Luckily, you don't have to drag yourself to an (often awkward) IRL in-store bra fitting, though a number of lingerie brands now offer virtual bra fittings too. Still not keen? Well, it's actually really quite simple to measure your bra size at home – and all you need is a tape measure.
“Wearing an ill-fitting bra may mean missing out on both comfort and support,” a Boux Avenue bra fitting expert tells us. “A well-fitted bra is about all-day ease and posture-perfect support. For those with a fuller bust, the right bra can make all the difference, helping to alleviate back strain by providing that much-needed and correct support to your bust, whilst enhancing your silhouette.”
With research suggesting that 90% (!!) of British women are actually wearing the wrong bra size, despite the obvious telltale signs, let's *finally* establish once and for all how to correctly measure your bra size at home. There's no shame in needing a refresher, especially with all the endless confusing information online, so allow us to make things a little simpler. Trust us, your boobs will thank you.
What are the signs you're wearing the wrong bra size?
If your bra doesn't fit properly, that means you're more than likely not getting the best form of support. You might also experience discomfort such as:
- straps slipping off or digging in
- gaping cups
- breast spillage
- underwire digging in
- tightness around your rib cage
- back and shoulder pain
- painful red indentations from your straps
Can your bra size change?
Yep, your bra size can change monthly thanks to factors including your menstrual cycle, and hormone fluctuations, while pregnancy, weight gain or loss and menopause can also contribute to differing sizes too. Plus, you may even be a totally different cup or band size in different brands, just like how clothing sizes aren't uniform across the high street. Helpful, right?
Even more reason why it's worth measuring your bra size each time you shop for a new bra. “Make regular fittings part of your self-care ritual,” suggest Boux Avenue, “because you deserve to feel supported, uplifted, and sensational!” If you can go in-store and get professionally measured at a speciality retailer like M&S, Boux Avenue or Victoria's Secret, that's one way to do it.
But if you're pressed for time, or simply don't fancy a stranger getting that up close and personal, we've got some handy at-home measuring instructions right here. All you need to figure out your bra size at home is a tape measure and a piece of paper (or your Notes app) to jot down your measurements as you go.
How to measure your bra size at home with a tape measure
First up, measure your band size. The band of your bra should sit directly underneath your boobs. Depending on what style you end up purchasing, the thickness will vary based on how many rows of hooks are on the strap.
While braless, bring the tape measure around the top of your rib cage, just below where your bra would usually sit. Pull it snug, but not too tight, and take the measurement in inches. Write it down because we'll come back to it in a second.
Whatever number you got as your measurement (e.g. 32), we're going to add another number to that. So, if you got an even number as your measurement, you're going to +4, or if you got an odd number, +5. E.g. if your original measurement was 32, it would be 32 + 4 = 36 and that's your band size. Easy, right?
To measure your cup size, wrap the measuring tape around the fullest part of your chest, and write down the measurement to the nearest whole number. Again, we're working in inches here.
Now subtract your calculated band size from step two (e.g. 36) from the bust measurement you've just done. We know, we know, maths was never our favourite school subject either. For argument's sake, let's say your cup measurement was 40 inches.
The difference in inches equates to its respective letter of the alphabet which determines your cup size. E.g. 40 inches (bust) - 36 inches (band) = 4 inches. D is the fourth letter of the alphabet, so your bra size translates to a 36D.
If you're still confused, check out our helpful video on how to measure your bra size below:
And, if all that *still* sounds too complicated, why not check out Nudea's Fit Tape? It makes measuring your bra size at home *so* much easier, no complicated adding or subtracting required. And the best part, with every purchase, you get a complimentary Virtual Fitting to learn how to properly use the bespoke tape from one of the brand's bra experts.
How do bra sizes work?
It might be worth clarifying at this point that if your band size changes, your cup size will change too, and vice versa. This is because the cup volume adjusts with the band size. Sure, your band size is a direct translation of your underbust measurement, but your cup size is worked out in relation to that and in simplified terms, is the volume of your bust to the size of your torso. Even though someone who is a 30C and someone who is a 36C both wear the same cup size, they have noticeably different bust sizes.
What is a bra sister size?
There may be occasions where you need to move up or down a bra size, depending on the brand and/or style. This is called sister sizing. While everyone has a true size, sometimes a bra in that size doesn't fit as well or as comfortably as you might like. Opting for an alternative bra size where the cup volume stays the same is a great solution.
If you're wondering how to move up and down cup sizes, it's pretty simple. If you move up 2 inches on the band (e.g. 36 to a 38), go down a cup size (D cup to a C cup). Conversely, if you want to go down a band size (e.g. 32 to a 30), go up a cup size (AA cup to an A cup). Most bra fitters recommend sizing one up or one down – any more than that and the proportions of the bra will have changed so much it will no longer reflect your true size.
How to measure your bra size without a measuring tape
Don't worry, if you don't have a tape measure to hand, all hope is not lost. Simply find a piece of string, ribbon, or maybe even your dressing gown belt that will wrap around your body.
Repeat the steps above, but make sure to mark on your measuring device at what point the ends meet. Then, simply lay it flat and measure the distance with a ruler or hard tape measure to find out your bust and underbust measurements.
Signs your bra fits properly
Once you think you're happy with how your bra fits, Boux Avenue's bra fitting experts have helpfully listed a few things to check to be super sure:
The bra feels secure on the loosest hook. Your bra will lose its elasticity over time, so starting on the hook that gives the biggest band means that you can tighten it when you need to, rather than realising it's too big when it's too late. This lengthens the lifespan of your bras, which is helpful if you've invested a lot of money in them.
The underband isn't rising up your back. The underband provides 80% of the support and therefore needs to stay in place when moving. Ideally, it should be in line and level all the way around your ribcage.
There is a finger-width of space underneath the band. A good indicator of whether your bra fits you properly is how many fingers you can slide underneath the band. A well-fitted bra should be snug, and only let you slide one finger under it. Tighten your band first, then move on to the straps.
Your straps feel fixed in place but don't dig in. There's nothing worse than pulling your bra straps up 100 times a day. They shouldn't be so loose that they fall down, but you don't want them too tight that they dig in. The straps should be the perfect Goldilocks in between – taut enough that they stay on the shoulders.
The centre front of the bra should sit flush against the breastbone. This part of the bra should be positioned centrally between your bust, offering separation of the cups. There should be no gaping between the bra and your chest.
Follow all of these steps and you'll be on your way to some well-deserved, well-cupped boobs thanks to a bra that fits properly. If you needed an excuse to hit ‘purchase’ on that lingerie set that's been sitting in your cart for months... you're welcome.
Let's go bra shopping!
Blessed with big boobs?
Maddy Alford is the Fashion Editor at Cosmopolitan UK and Women's Health UK, covering fashion content online and in print. Maddy specialises in shopping galleries and first-person reviews of the best fashion buys, from jeans and jewellery to wedding dresses, gymwear, and winter coats. She also writes op-eds on on pop culture, viral fashion moments, travel journalism, fitness, and the LGBTQ+ community's relationship with style. Maddy is also a fashion stylist who has worked on over 100 photoshoots at Hearst, including those starring Raye, Niall Horan, and Lena Dunham. Previously, she has worked in fashion PR and e-commerce, including stints at ELLE US and UK, Net-a-Porter, InStyle, and Time Out New York. Maddy has ten years of experience in the fashion industry in both London and New York City, after graduating with a Bachelor of Arts in Journalism. She is passionate about second-hand shopping, inclusive fashion, running on Regent's Canal, and finding London's cosiest pubs.
Alexandria Dale is the Digital Fashion Writer at Cosmopolitan UK. Covering everything from the celebrity style moments worth knowing about to the latest fashion news, there’s nothing she loves more than finding a high street dupe of a must-have designer item. As well as discovering new brands, she’s passionate about sustainable fashion and establishing the trends that are actually worth investing in. Having worked in fashion journalism for six years, she has experience at both digital and print publications including Glamour and Ok!
