Chances are your favorite bra from 10 years ago isn’t still your favorite bra today. Bodies change over time, and for many women, breasts change most of all. Weight gain, weight loss, pregnancy, cancer, surgery--reduction or augmentation, each of these factors can alter your bra size dramatically. Not only that, but women can expect to experience any number or combination of these phenomena over the course of their lives. 

And yet, one of the best things you can do is honor your body in its current state, and get it moving at whatever pace it’s capable of. If you have breasts, a prerequisite might be to make sure you’re wearing the right-sized bra. (Power to women who opt for no bra as the best bra. However, if you’re gearing up for a 10K, now might not be the time to #freethenipple.) 

So, boobs change from year to year (even from month to month), and it’s important to recognize and accept that by providing your girls adequate coverage and support whenever necessary. But how? We’ll cover everything from sports bra sizing to construction considerations below.

How to Determine the Right Size Sports Bra

The two main barriers you’ll encounter on your journey to find a well fitted sports bra are inconsistent sizing/fit guides and your continually changing size. The silver lining? Both of these challenges have the same solution: take new measurements every time you purchase another sports bra and be sure to try it on in-person for the best fit.

Most online fit guides and calculators will instruct you to take two measurements: one just below your bust line, and a second around the widest part of your bust. (Note: this may not necessarily be across your nipple line!) Your underbust, sometimes referred to as your ribcage measurement, will determine your band size, while the difference between the widest part of your bust and your underbust will be used to calculate your cup size. Some fit calculators include a third measurement just below your armpits. The most important thing to remember is that you must use the designated size chart for each brand to determine what size you may be in their styles. It’s rare, if not impossible, to be exactly the same size across multiple brands because of the large variation. 

How Should A Sports Bra Fit?

A sports bra should fit slightly more snug than your everyday bra, which is intuitive as it will be subject to more intense activity and movement. That being said, a sports bra should never be so tight as to constrict your breathing or leave behind permanent marks. It should fit snugly, but not too snugly. When your sports bra is on, there should be room in the band for an extra finger or two, but no more. Just like your everyday bra, the band will be doing much of the supporting work, but there’s also a reason you’ve never seen a strapless sports bra. The band holds your bust up, but the straps (as well as the general compression of the bra) will also help reduce movement and hold the bra in-place while you're active. When in doubt: the thicker the band and the thicker the straps, the more support they will provide. Bonus points if the straps are adjustable! This will allow you to have even more control over the fit of your bra. It’s also important if you’re tall or petite because bust and rib cage measurements don’t take into account the length of your decolletage.  


If use of a brand’s sizing/fit guide does not result in a well fitting bra, a “sister” size may provide a better fit. So, it is useful to know both of your “sister” sizes. These can be easily calculated by going up one cup size and down one band size, or up one band size and down one cup size. For instance, if you’re a 34C, you might also fit into a 32D or a 36B depending on how tight the band runs, or how large the cups run. 

If the cup of your sports bra is gaping and the band is tight, you should consider sizing down in the cup and up in the band, and if the band is loose but the cup is tight, size down in the band and up in the cup. (Note: a band that is too loose may ride up in the back, while if it’s too tight, it will dig in and possibly leave marks.) 


Find the Right Level of Support

In simple terms: the higher the level of activity you plan to engage in, and the larger your cup size, the higher level of support your bra should provide.

With maybe the long jump (or traveling to space??) being the highest level of impact… It’s good to have at least a few bras in rotation so that you have a few to meet your energy level for any given day. If you’re feeling peppy, maybe pick a bra with a higher level of support! And if you’re running errands or working from home, maybe pick a bra that prioritizes comfort instead.

Most bras have their own product information to help you determine if it will be up to snuff for the activities you have planned, but as stated above: bras with thicker straps, hook-and-eye closures, and adjustable arm straps will generally provide more support for larger busts and/or higher intensity workouts. Thinner bands with strappier and less compressive designs will provide less support.

Sports Bra Materials, Construction & Features

Most sports bras are made of a blend of either polyester or nylon with spandex. Both polyester and nylon serve to make the garment more durable, while spandex increases elasticity for stretch and recovery. But regardless of composition, there are three main categories of sports bras: compression, encapsulation, and a hybrid of the two.

Compression bras do exactly what the name says: they compress your breasts to the chest wall, thereby restricting bounce and movement. The downside here is that compression bras only have one pocket, thus they often give rise to uniboob. They also tend to be less customizable: their straps are rarely adjustable, and they often come in alpha or numeric sizing, both of which are less specialized than cup sizing.

Encapsulation bras, on the other hand, are what you picture when you think of a classic, everyday bra. They have two cups to keep the breasts separated, lifted, and supported. They provide a more “natural” look, but tend to offer less support unless designed specifically for high impact sports. It is also worth noting that few sports bras will truly be “encapsulation only”--by definition of being a “sports” bra, most will provide some level of compression, and the amount of compression the bra offers will determine which activities it’s marketed for.

If you have a larger bust, are engaging in higher-impact activities, or both, a hybrid compression-encapsulation bra will likely be best for you. This is because you can ensure a more accurate fit with their cup sizing, and they tend to be more stabilizing as they compress each breast individually, rather than both at once.

How Long Do Sports Bras Last?

The rule of thumb is to replace your sports bra every 6-8 months, or at the very least, every year. (However, this will depend on a few other factors like: frequency of wear, frequency of wash, level of support required, and intensity of workout.) To put this into context, you’re supposed to switch out your running shoes every ~400 miles, or every ~5 months if you’re running 20 miles a week. So, if you’ve switched out your trainers once or twice without giving a second thought to your sports bra, it might be time to consider a replacement. Just like worn tread and wrinkles in your soles are indicators of wear and tear for your shoes, there are a few signs to look for when it comes to a worn out sports bra. There may be loosening of the band or straps, the fit may become more comfortable and less compressive, and you may find your chest is bouncing more than it used to. All of these signs indicate that it is time for you to get fitted for your next sports bra, as your old one has merely worn out, or your body has changed enough that it’s no longer fitting properly.

Some notes on caring for your sports bra

When you’re having a slow, lumbering run through your neighborhood, it can be easy to feel like a bit of a fraud. But never fear! Something that never fails to reassert your identity as a Runner is that dirty pile of discarded gear growing inside (and sometimes outside!) of your hamper. And actually, there may be slight cause for concern here. Depending on how long it takes you to get around to washing those clothes, sweat can start to break down fibers and weaken the structural integrity of your activewear–not to mention the fact that it will certainly make them stink. So, especially when it comes to your sports bra, it might be time to make doing laundry your new favorite. If you don’t have enough dirty clothing to justify washing an entire load, consider hand washing your sports bras in the sink. Then you can put them in the machine on a quick spin cycle so they’ll dry faster. And you should always line-dry your sports bras. The heat of the drier can break down the elastic fibers, which means your bra won’t retain its structure and will need to be replaced even sooner. So, save yourself some money and hang your sports bras up to dry!