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How to Measure Bra Size the ThirdLove Way

How to Measure Bra Size the ThirdLove Way

portrait of Heidi Zak
Heidi Zak
Co-Founder & Co-CEO

Getting measured for a bra is historically an unpleasant and awkward experience that typically goes something like this: you visit a chain retailer or department store, a salesperson measures you in a dressing room, and you walk away with a bra that probably doesn’t fit. In fact, 80 percent of women are wearing the wrong bra size.

So how can women accurately measure their bra size? Below we break down bra sizing both the traditional way and the ThirdLove way, and offer advice on how to find your perfect fit at home.

ThirdLove's full coverage bra in nude
ThirdLove’s Perfect Coverage bra in Taupe.

Traditional Bra Sizes Explained

Bra measurements are calculated based on your band size (number) and cup size (letter). Traditionally, you or a sales associate would wrap a tape measure around your rib cage (right below your breasts) and bust (the fullest part of your chest) to determine your bra size. But oftentimes, the issue with using this method is that it requires rounding up to the next even number in inches.

As you might imagine, this leaves out a significant population of women who fall in between sizes. Rather than forcing women into a standard cup size that doesn’t fit, we take into account your unique breast shape and fit issues and even invented our signature half-cups to help you find your perfect bra.

The Importance of Knowing Your Sister Size

Your breast shape, band size, and cup size rarely fit neatly into a single letter and number. For example, a DD cup size is equivalent to an E cup while a DDD cup size translates to an F cup — but the cup volume depends on the band size. This is where your sister size, or bra-size equivalent, comes in which can help you find a better fitting bra.

“Sister sizing is when you have the same cup volume and different band size,” said Erica Johnswick, ThirdLove’s Customer Experience Outreach Lead. For instance, if you find that a 34C fits great in the cups, but the band is too tight, you’d need to adjust both your band and cup size to a 36B. Remember: Any time you go up a band size, you need to go down a cup size, and vice versa. Use our helpful Bra Size Chart as a sizing guide.

How to Find Your True Bra Size

It’s likely that your current bra size is outdated, to say the least. Women’s breasts can change size six times over the course of their lives whether it’s due to pregnancy, weight changes, or other factors. So let’s check-in to make sure you’re still getting a proper fit.

Here’s our advice for measuring yourself the ThirdLove way:

1. Identify your breast shape.

Using our Breast Shape Dictionary, see which category best describes your unique shape: Asymmetric, Athletic, Bell Shape, Relaxed, East West, Round, Side Set, Slender, or Tear Drop. This will help us to recommend the best bra style for your unique shape.

2. Be honest about any fit issues you’re having.

Check out these common bra fit issues to get a good idea of what your current fit issues are. Identifying common problems, like gaping cups and slipping straps, can help us determine which size bra you should actually be wearing and whether you need to go up or down a size (or half-size). Also, watch our Fit Expert, Ra’el, walk through how a bra should fit on the body.

3. Find your favorite cup type.

Some women prefer a wireless bra while others need more coverage. Some hunt for the perfect t-shirt bra while others feel better in a lace balconette bra. Check out all of the most common bra styles to find out what you like.

4. Try our Fit Finder® quiz.

50 percent of women between A and E cups don’t fit into a standard cup, so we developed half-cups and our Fit Finder™ to help those “in-betweeners” find their perfect fit. Just answer a few questions based on your breast shape, style, current fit issues, and other factors to discover your results. One in two women ends up wearing a new size and falling into one of our half-cups when completing the Fit Finder® quiz!

Learn more about our collection here.

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