How to Find the Best Sports Bra for Running Based On Your Bra Size

How to Find the Best Sports Bra for Running Based On Your Bra Size

Have you ever wondered about the importance of wearing a sports bra when running? A study by the University of Portsmouth reveals that it's paramount that you do. According to the study, wearing ill-fitting bras that fail to restrict the side-to-side movement of breasts and offer adequate support can damage your tissues and ligaments. The researchers also confirmed that the quality of the bra affects your running style and shortens your stride.

Therefore, choosing a good sports bra for running should be a priority for any female runner, not an oversight. Now that you understand the importance of wearing a perfectly-fitting sports bra for running, let's learn how to pick the best one.


Should a Sports Bra be the Same Size as Your Regular Bra?

Most companies only provide sports bras in alpha sizing (XS-XL, ect) but at ThirdLove, we provide our high impact sports bras in regular cup-band sizing for the ultimate support. Whether you’re purchasing an alpha sized sports bra, or a regular bra-sized sports bra, you’ll need to know your exact measurements to find the perfect fit. Here’s how to find your sports bra size in a few simple steps.


How to Measure Your Cup Size

Step 1: Measure around your rib cage by placing a measuring tape beneath your breasts. You should hold the tape snug so it doesn’t fall down, but loose enough to slide two fingers underneath comfortably. If the measurement is even, add 2 inches, and if it is odd, add 3 inches. This is to account for the size difference when the elastic band is stretched or relaxed. This is your band size!

Step 2: Place the measuring tape on the fullest part of your breasts, usually near the nipple. Don't forget to hold the tape slightly loose, just like you did earlier. Note down your bust measurement.

Step 3: Find your Cup Size by subtracting your band size from your bust measurement. A difference of 0 inches is considered an AA cup, and for every inch, you want to increase 1 cup size. So 1 inch would be A cup, 2 inches would be B cup, 3 inches is C cup, and so forth. If you’re in between cup sizes, we offer half cups as well for the perfect fit!

If you would like some more help finding your perfect bra size, take our quick online Fitting Room Quiz to find your perfect size and style in just a few questions. And for additional help, always feel free to chat with and ask any of our fit stylists!


ThirdLove's sports bra.

Picking the Right Level of Support

You learned how your breasts move up, down, and sideways while running, making the right level of support a high priority. Remember that the type of activity and your cup size usually determine the level of support you need. Also, remember that smaller-chested ladies might get away with medium-impact bras for even running, but those with larger busts require more support, even for less intense activities.

Let's learn more about the levels of support different bras offer and how to choose the best sports bra for running.


Low-Impact Sports Bras

Low-impact sports bras provide gentle support for walking, yoga, and weightlifting. Typically featuring removable cups, little to no padding, and thinner shoulder straps, they are generally lightweight.


Medium-Impact Sports Bras

Featuring built-in or removable cups and wider bands, medium-impact sports bras offer moderate support. These are more suitable for activities such as cross-training and hiking, although you should consider your cup size before deciding.


High-Impact Sports Bras

High-impact sports bras for women come with defined cup structures, thicker bands, adjustable straps, and padding to maximize support and encapsulation. It's recommended that medium to large-chested women wear high impact sports bras when running and for activities such as mountain biking and aerobics.


ThirdLove's racerback sports bra.

Picking the Right Style

There is a wide range of sports bra styles. It's important to remember that their designs not only dictate their appearance but also their feel, fit, support, and versatility. As a result, the best sports bras should align with the support and comfort you need for running, not only appearance.



These bras feature a "Y" shape in the back, enabling more freedom of movement and preventing straps from sliding off your shoulders during running. Typically available in XS to XL sizes, racerback sports bras are an excellent option if you have a smaller bust.



The straps of cross-back bras meet in the back in a cross shape, enabling a wider range of motion. These comfortable sports bra designs generally come with some adjustment to ensure a secure fit, preventing the straps from slipping off while running.



The design of scoop-back bras is similar to the design of your everyday traditional bra. Many larger-breasted women prefer scoop-back sports bras since they are easier to take on and off. Scoop-back bras also offer a range of padding options to suit the appearance and support you're looking for.



As the name suggests, you can easily remove the cups or "cookies" from these bras, providing versatility, ease of use, adequate support, and modesty. You can enjoy free reign on the cookies you use with individual and one-piece inserts.

Sports bras with removable cups are an excellent option if your breast volume increases during menstruation since you can remove the cups to create extra room for some comfort during that time of the month. Similarly, you can add padding to increase coverage when running in cold weather.



This sports bra style is perfect for complementing the natural beauty of your breasts with the cup separating each breast, offering targeted support. Built-in bras are also easy to wash since you don't need to worry about removing cups before washing.



These bras press your breasts against your chest and don't feature any padding. This could result in a tighter fit but with less support. As a result, these might not meet the cut for running, even if you have a smaller bust.


How to Choose the Perfect Sports Bra for Running

The perfect sports bra for running should provide exceptional support, coverage, and protection to your breasts without applying undue pressure on your chest or back or negatively affecting your form while running. You should feel confident about its performance and appearance so that you can focus on running.

The ideal sports bra should be snug - tighter than your everyday bra - without being uncomfortable or restricting. When wearing the sports bra, the cup should not have gaps or wrinkles, and your breasts should not be spilling out. Finally, the sports bra, including the straps, shouldn’t move around when you move or limit your movement in any other way.


Women’s Sports Bras

Finding the perfect running bra might be much more complex than imagined. The good news is, we know your needs and concerns and have designed the best sports bras for all sizes!


ThirdLove's flex sports bra

Flex Seamless Racerback Sports Bra

This cute Flex Seamless Racerback Sports Bra combines comfort and support with wireless, removable soft cups and seamless knit zones. The stylish racer-back is ideal for small to medium cups for running, cross-training, and other activities of similar intensity.


ThirdLove's Kinetic high impact sports bra.

Kinetic Adjustable Sports Bra

Here's an adjustable sports bra that provides ultimate support for medium to large cup sizes to crush those running goals. Available in cup-band sizes for the ultimate support, the Kinetic Adjustable Sports Bra comes with wireless comfy built-in cups for optimal coverage, adjustable straps to ensure a perfect fit, and tagless back closure offering stable compression and support. The versatile two-in-one design enables you to change styles according to your liking.


We hope this article helped you to understand how to find the best sports bra for running. We also understand that it can be difficult to find a perfect sports bra online as you don’t have the ability to easily try it on. That’s why we offer easy returns and exchanges so that you can try your sports bra on in the comfort of your home and try moving around before deciding if it works for you! Crush your goals, not your girls, with ThirdLove!