How to Determine Your Bra Size: A 4-Step Guide to Finding Your Perfect Fit

How To Find Your Correct Bra Size

1. Measure Your Band Size

Take a measuring tape and wrap it around your ribcage just below your breasts. Use a mirror to ensure the tape is parallel with the floor. Write down the nearest even number in inches. If you’re halfway between two numbers, write down the larger one.

2. Measure Around Your Bust

Wrap your measuring tape around your boobs at their fullest point. For most of us, this is in line with your nipples. Ensure that the tape is parallel with the floor before writing down the nearest whole number once again. 

3. Subtract Your Band Measurement From Your Bust Measurement

Let’s say your first number is 38 and the second is 43. Subtract 38 from 43 to get 5, which corresponds to a DD cup size. How’d we get to a DD? You can either refer to the handy chart above or count up starting with 1 for an A cup, 2 for a B, 3 for C and so on.

4. Combine Your Band Measurement With Your Cup Size

Et voilà! This is your bra size. So if we take the example above, you’d end up with a size 38DD.

Additional Fit Information To Keep In Mind

As we mentioned earlier, your band and cup numbers are, unfortunately, not the be-all and end-all in bra sizing. Some fit issues stem from wearing different styles or types of bras, adjustments to the straps or even size discrepancies across brands. (In my experience, Victoria’s Secret bras fit best when I size up while I find that I have to size down at Aerie.) So in order to properly narrow down what to look for when shopping for new brassieres, here are some additional pieces of information to keep in mind.

1. Most Of The Support Comes From The Band, Not The Straps

Contrary to what you might have thought, the majority of support comes from the band. This is why strapless bras work even without the generous aid of straps. The band needs to fit pretty snugly against your ribcage in order to do what it’s supposed to. With a properly fitting band, you should only be able to slip two fingers between it and your body.

2. Your Sister Sizes Might Actually Fit Better For Some Brands

What is a sister size, you ask? Every bra size corresponds with two other sizes that will fit just about the same as your true size. It works by either going up one band size and down one cup size to find your larger sister size, or going down one band size and up one cup size to find the smaller. (So, for example, the sister sizes for someone wearing a 36D would be a 38C and a 34DD.) For certain lingerie brands, your sister size might actually be more comfortable and fit better than your true size, so you might want to try on a few the next time you hit the dressing room.

How To Tell If Your Bra Fits

OK, so you know your correct bra size, you’ve learned all about sister sizing and the shape of your breasts, now it’s time to actually put a bra on. Before you go and drop a ton of money on a whole new lingerie drawer, try on your favorite bras once more and see if maybe all you really needed to do was adjust the straps or use a different hook. Here are six signs your bra fits perfectly.

1. The Band In The Back Is Level And Even With The Band In The Front.

If it’s too low, tighten the straps. If it’s too high, loosen the straps.

2. The Straps Aren’t Digging Into Your Shoulders.

Similar to the band, your straps should fit snugly on your shoulders so that they won’t slip off but shouldn’t be leaving uncomfortable marks or digging in.

3. Your Breasts Sit About Halfway Between Your Shoulders And Elbows.

Look at yourself sideways in a mirror to see where your girls are hanging. If they’re too low, you probably need to find a more supportive bra.

4. There’s No Gapping Or Spillage At The Cups.

Put on a slim-fit top or T-shirt to get a better idea of this one. If it looks like your breasts are pouring out of the cups, you should try going up a cup size. On the opposite end, if the rim of the cup is very prominently showing through your top, you should go one size smaller.

5. The Center Gore And Any Underwires Lay Flat Against Your Sternum.

Remember how we said you should be able to stick two fingers in between the band and your body? This is not true for the center gore (that quasi triangular piece right between the cups) or the cups themselves, especially if you’re wearing an underwire. They should lay perfectly flat without digging in or pinching anywhere.

6. Always Use The Outermost Hook When Trying On Or Wearing New Bras.

Your bra will stretch and loosen over time, but if you’re already using the tightest hook then you’ll be out of luck and stuck with a band that’s too big. Start with the loosest hook so that you can get as much wear out of your bra as possible, even once it starts to stretch out.

Now go forth and arm yourself (and your girls) with the best-fitting bra of your life. Here are a few PureWow favorites to get you started.

Our favorite brands: Aerie; Wacoal; ThirdLove; Lively; Cacique; Calvin Klein; Journelle