How to Measure Sports Bra and Size

Shopping for bras is almost never an easy undertaking. It gets even more complicated when you start to shop across different brands and styles.

For the most part (although different brands do different things), sports bra sizing is similar to standard bra sizing. However, as you read on, we’ll make it clear that relying on your own at-home measurements isn’t going to set you up for success every time.

Why Measuring Yourself Isn’t Always Reliable

If you’re shopping for a sports bra size, you may notice that many brands don’t observe the standard bra size (e.g., 36C) but have sizes ranging from 1-4, or run small, medium, large, etc., which can confuse you even more.

Think of it this way: When you go jean-shopping, do you find yourself able to wear the same size in every brand and style of jeans? No, right?! Much as it sucks, there’s something to be said for trying every pair on. 

Sometimes, you can even be surprised that a style you love on the hanger you hate in real life. Because not only are there differences across bra brands, every woman’s body is different too. That’s why we recommend getting fitted instead of relying blindly on your own measurements. 

Good news: You don’t have to leave your house to get professionally measured at Knix!

Getting Your Sports Bra Size Right: What to Expect from a Knix Virtual Fitting

• Book your virtual fitting here to find the right sports bra size
• We’ll connect you with one of our expert Knix team members for a 1-on-1 fitting session over video chat. 
• To find the right sports bra, we recommend you come to your fitting wearing a non-padded bra and a fitted t-shirt to ensure we get an accurate measurement. You’ll also need either a) a soft measuring tape or b) a piece of string or cord and a tape measure or ruler.
• With different styles and sizes for 30A to 42G in the world’s most comfortable and supportive wireless bras, our fit experts can help you get into something that you will love to wear every single day.

The Most Important Sports Bra Consideration: Impact Level

When you shop for sports bras, you’ll sometimes notice that brands indicate “impact level” on different styles.

Impact level refers to the amount of movement (and therefore bounce) your activity entails. For example, running, jumping, dancing are considered high-impact while lifting weights is sometimes low or medium-impact.

Note: Impact doesn’t reflect how good a workout you get (weightlifting is an awesome workout, you just won’t bounce around as much doing it as you do with other sports).

Here’s a handy overview of exercises x impact level:

It’s worth noting that if you have larger breasts (greater than a C cup), you might consider wearing a high-impact bra even for low to medium style activities, as you probably need more support in general.

Another Important Consideration: Sports Bra Styles

Now that you’ve considered your size and impact level, it’s worth looking at the different styles of sports bras. In general, there are 3 designs:

1. Compression

Compression bras focus on doing precisely that - compressing your boobs against your chest wall, so they lie as flat as possible against your body. By compressing you, they minimize movement and bounce.

However, compression bras do not have cups built-in for each breast and can also cause an appearance of “uni-boob.” Many women won’t be bothered by this, but others will want to preserve their breast shape even when working out.

2. Encapsulation

Encapsulation bras do have cups that surround and shape each breast. There is generally no compression with these bras, which makes them ideal for low-impact activities.

Because each breast is “cupped,” encapsulation bras do a good job preserving your natural body shape.

3. Encapsulation-Compression

Don’t want to choose? You don’t have to. There are bras that do both! These bras usually have an inner layer that provides cupped support and an outer layer or band of material that compresses your boobs against the chest wall.

These bras provide the best-of-both-worlds in terms of both appearance and support and can be good for high impact levels of exercise and all sizes of chest.

Other Sports Bra Features to Consider

In addition to compression or encapsulation as types of bras, there are other features that provide more options for you. Depending on your size, style, and exercise impact level, some of these features may be more important than others.

• Adjustable straps: Adjustable straps allow you to lengthen or shorten straps depending on your torso size and shape. For larger bust sizes (C cup and above), adjustable straps are more important as more support is required.
• Strap style: As sports bras have become more fashion-forward (and are often worn revealed, or even without tops), different styles of straps have emerged. There’s the traditional tank top style (often a pullover bra). There are also racerback—if you experience slipping shoulder straps a lot, you may love this style. There are also crisscross straps that make a bigger style statement.
• Underwire: As with regular bras, sports bras come with and without underwires. While underwire is often considered to offer more support, it can also be uncomfortable for many women. Underwire bras are also more likely to require handwashing. With many technical fabrics and designs on the market, an underwire is a personal choice rather than a support necessity.

The Best Knix Sports Bras for Every Person

Best Overall for High Impact Bra for Running: Catalyst Sports Bra

The Catalyst Sports Bra is the most supportive, high-impact, wireless sports bra you’ll ever put on. Designed to drastically reduce breast movement, the Catalyst outperformed over 800 bras it was tested against. And taking it off after a long workout is a snap!

What reviewers say:

“As a fitness instructor with curves I HATE all the sports bras out there as they always make me look like my chest is pushed in and tube-shaped. Not the catalyst, Best support and shape I have ever had. I'm in LOVE. (tight at the beginning but stretches to perfection very quickly)”

“I love this bra. I have a large chest and it holds up to HIIT workouts and is really soft and comfortable.”

Size options:

32A to 42G - and everything in between!

Best Zip Front: Catalyst Front Zip Sports Bra

The most supportive sports bra ever and even easier to put on and take off. The front closure, cross-back high-impact Catalyst Front Zip Sports Bra gives you the wireless support, comfort, and adjustability you want—without the painful struggle.

What reviewers say:

“I have been endlessly looking for a cute but comfortable and supportive sports bra for years. I have tried (what feels like) every option under the sun and the Knix Catalyst and Knix Catalyst front zip sports bras are hands down the winners! Pricey but absolutely worth the investment in my opinion. I workout 5x a week - a combination of HIIT, spin, and strength workouts - so a bra that keeps my chest supported is so critical. These bras are definitely it and provide the support I need to feel secure during my workouts... I LOVE THEM!”

“I ordered this bra for riding and skiing. It's solidly built and comfortable. I love the fact that it closes in the front and the back. It's pretty enough that I might even wear it in summer, as a top for biking.”

Size options:

32A to 42G - and everything in between!

Best Sports Bra for Low Impact Exercise or Working from Home: LuxeLift Pullover Bra 

With sizes 28A to 44G, enjoy the unbelievable support and feel of LuxeLift Technology in the super versatile and easy-fitting LuxeLift Pullover Bra that feels like you're wearing nothing at all. Sure to be your new go-to option and everyday low impact sports bra.

What reviewers say:

“Super comfortable, supportive, easy to get in and off, and I didn't need a "break-in period.”

“It’s the most comfortable and supportive bra I’ve ever owned!”

Size options:

28A to 44G - and everything in between!

How to Evaluate the Fit of Your Sports Bra

When you try on a sports bra, you’re looking for slightly different things than when you shop for a regular everyday bra. Here are some of the things to really look for:

• Support: Obviously, support is the point of all bras, but really test it with a sports bra. Do a few jumping jacks and make sure you feel supported and confident. Your sports bra should be smooth across your bust and back. Wrinkles are a sign that there’s excess fabric, so try sizing down.
• Coverage: While there are “sexy” sports bras that show cleavage, most of the performance-focused sports bras give you full coverage. There should be no cleavage or spillage with these sports bras. You should be fully and comfortably contained with no bulging above the cups or at the back.
• Comfort: Even if you’re not quite Serena Williams, you want to focus on your performance, not your bra. So you want a bra that doesn’t distract you. If straps dig in or feel too constrictive, or if the band is too tight on your rib cage, it may become painful and/or distracting once you hit the gym or field. Although sports bras always feel a little constrictive, they should never be painful or uncomfortable.

Caring for & Replacing Your Sports Bra

Once you have found the perfect sports bra, you’ll want to care for it properly. 

• Wash your sports bras regularly: We wrote a whole other article about washing your sports bras. But the general rule of thumb is that they require much more frequent washing than your everyday bras. This is because sweat can really break down the fabric.
• Keep a few sports bras in rotation: Because sports bras get warm and damp, they need time to “relax” back to their original shape between washes and workouts. So keep a few in rotation, and you’ll always have a clean and supportive bra.
• Look for signs that you need to replace your sports bra: A sports bra will last a year, or about 40 washes maximum. But don’t ignore signs that it’s time to replace. Those signs include: Damaged hooks, fabric pilling, elastic showing visible breakages, a general sense that the bra is no longer supportive (loosened steps, etc.) 

And remember, when it’s time to replace your sports bra, it’s an excellent opportunity to get fitted again and make sure you’re still in the best size and style for your body!

Written by Jane Flanagan — Updated on March 1, 2022.

We hope you found this post informative — but remember: we’re not doctors and this post is not medical advice! While all posts are fact-checked and well researched, we always recommend you chat with your doctor about any questions or concerns you might have regarding a medical condition. We’re here to support and educate, but never with the aim of disregarding professional medical advice you’ve been given. Phew, now that that’s out of the way, you can go on living unapologetically free.