This Bra-Size Calculator Is a Thing of Genius

Without the help of our bra-size calculator below, finding out (and updating) your bra size can be a time-consuming and downright annoying thing. There are loads of ways you get your bra fitted (and I do venture afield, as you'll see below), but the truth is that it's super-important to keep checking. Our bodies change quickly (weight can fluctuate and our figures shift all the time), and wearing the wrong-size bra can be rather damaging to your breast tissue. So although we would always recommend getting fitted properly, it is a great idea to be able to scope out your own bra size from home. That way, you can be on top of things when you're too busy to visit a lingerie department every six months.

The first thing you'll learn? You've probably been wearing the wrong bra size for a long, long time. But don't worry—you're not alone in that mistake. It's incredibly common for people to assume that they have bigger backs than they actually do (or be scared of having a larger cup size for the fear that it will limit their options). Here's where we step in to help.

To get some expert intel, I headed to both M&S and Rigby & Peller. The latter is an old-school underwear shop that works very differently from other stores. Instead of measuring you, the bra fitters work by sight. They just look at your chest and work out which size you are. Both Rigby and M&S came back with a 34D. Now, while just knowing someone's bra size from looking at their chest does seem like a sort of superpower every breast owner should have, alas, it's not something we can all possess, which is why I got thinking about a bra-size calculator. Additionally, since in-person bra fittings are not available at the moment (important note: I got fitted before COVID-19, which is why the aforementioned experience was in person), this bra-size calculator is an easy way for everyone to work out their own bra size without having to step foot in a store. Keep scrolling for our guide on how to find out your correct bra size, and you can thank me later.

Step 1: Band

To measure around the band part of your bust, which is directly underneath your breasts, make sure you have a soft tape measure to hand, place it flat against your skin, and draw it around your torso. Keep as close to under your bust as possible. Once you've done that, note down the number in inches.

Step 2: Bust

Once you've done the band, then you want to measure the fullest part of your bust. Gently take the tape measure and measure it in inches as well.

Then comes the slightly tricky bit: To work out what your cup size is, you want to subtract your band size from your bust size. From the difference between the two sizes, you can work out your cup. If the difference is less than 1, then it's AA, 1 means A, 2 means B, 3 means C, 4 means D, 5 means DD, and so on.

You'll still need your band measurement to give you the number preceding the letter. For example, if your band size is 34 but your bust size is 37, then your bra size is 34C (difference of 3, again, means it's a C cup). Of course, it's worth mentioning that bras can fit differently according to different brands, but now you have the basic tools to work out your correct size.

If you need more guidance, however, I also spoke to bra-fit expert Julia Mercer from M&S, who gave me some further insights so that if you ever want to know how to find the right size, you'll be in no doubt. First off, Mercer said that as the average bust size of women is growing (34B to a 36D/36DD in the last decade), "it's become more important than ever to wear a bra for both comfort and support."

Mercer also said, reassuringly, that you should "never be alarmed if you have to go up a cup size," as this will help your posture. And the best way to check if your bra is fitting correctly? "Lift up your arms twist your body, and the bra will fit perfectly in place," she advises. For more help, keep scrolling for a bra-fitting checklist.

5 Key Checks for the Perfect Bra Fit

1. Under-band: This should be parallel to the floor and secure enough that only two fingers can fit under the elastic.
2. Center front: Should sit completely flat against the sternum.
3. Side wire: Make sure this is flat against the rib cage and never digging into breast tissue.
4. Cup capacity: Breasts should sit fully into the cup without any spillage.
5. Straps: These should be adjusted to just fit two fingers on top of each other under the strap, which will give the right pressure for your shoulder.

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This post was originally published on Who What Wear UK. Want more? See our body-shape calculator that is guaranteed to make all your clothes look amazing.