Experts bust the 5 biggest myths about bras, which no lie, will change how I shop

My bra situation is pathetic. I can’t believe I’m admitting this to the public, but I really only wear one bra every single day. Needless to say, my intimates drawer could use some work, and the more I learn about how to find a bra that fits (actually fits rather than kind of works), the more I realize that so many different factors go into finding the right bra. The problem with this? Plenty of people are walking around with not enough support, something that should’ve been retired, or something that’s entirely the wrong size.

It’s something that Frederika Zappe, national fit specialist, witnesses everyday. “I would say eight times out of 10 when someone comes in to be fitted for a bra, she is invariably wearing her band too big or the cups too small,” she says. Case in point? My entire life, I figured that because I am small chested, I should be wearing a 32A or 34A. But… I’m actually a 28C. Whether you’re looking at your everyday bra or one for the gym, experts break down the most misunderstood aspects of bras and how they should fit that you should know about for your best support ever.

The support is in the band

The two main parts of a bra that keep it in place are the straps and the band, but it’s the band that does the real heavy lifting. “Eighty percent of support come from the bottom band—straps do nothing,” says Heather Cvitkovic, director of apparel merchandising at Brooks Running. “If you’re getting proper support from the bottom, your straps should not be working very hard.” In fact, if your straps are always falling down or digging into your skin, she says it’s a sign that your bottom band isn’t fitting right. In other words: This is another reason why it’s important to know your proper bra size. (Because, real talk: Nothing is more annoying than uncomfortable bra straps.)

Where your bra sits matters

I had always figured that once I managed to get my bra on, it was good to go. Nope—where it sits on your body makes a difference in how it supports you. “Take your two thumbs and reach back and press on the outside wire of your bra,” says Zappe. “That should be sitting behind the breast tissue on your bone. The front end of your bra should also be on your rib cage. So every bit of your breast tissue should be sitting within that wire ‘smile.'” The term ‘smile’ comes from how your bra should look: It has to be wide enough to encompass all of your breast tissue, which goes all the way into your back, she explains. “Most people carry a lot of breast tissue underneath the armpit, and all of this needs to be in front of the underwire, which happens if you are wearing the right size cup,” she says. And she adds that the band in the back should be parallel to the floor—not riding up.

Your bra size changes

Fun fact: Your bra size isn’t like your shoe size—it fluctuates. “Don’t assume that you are the bra size you once were,” says Julianne Ruckman, senior product line manager at Brooks Running. “Our bodies change so frequently that it’s important to get re-fit or try on multiple sizes to ensure the best fit for your body today.” Cvitkovic agrees, saying that it’s important to get a bra fitting once a year to make sure you get proper support.

Bra sister sizes are a thing

If you can’t find your exact size when bra shopping, look for your bra’s sister size—or the size equivalent in varying size and cup. “Sister sizes are cross-graded sizes where the cup volume stays the same even though the cup letter changes,” says Ruckman. “For example, a 34C has the same cup capacity as a 30DD, 32D, 36B, and a 38A. It’s a little hard to believe, but it could help you in a pinch. ” Essentially, the most important thing is to find a cup that fits you snugly. “If you love the fit of a cup, but the band feels too big, then the sister size solution would mean you’d decrease the bottom band first, then go up in the letter of your cup to maintain the same volume,” she says. And vice versa, which opens up a whole new world of options when shopping.

Bras have a lifespan

“A bra should never celebrate a birthday,” says Cvitkovic. (Whoops.) “Ideally, you should have one in the wash, one in your drawer, and one on your body,” she says. That’s because your bra goes through a lot, and plenty of things break it down. “If you wash it warm and dry, it breaks down spandex. Sweat and dirt can break down fibers of a bra, too,” she says, making the case for having a bra wardrobe (this all applies to sports bras, too). “If you follow the recommended wash, you’ll get a longer lifespan out of your bras.” I don’t know about you, but I have some bra shopping to do.

To help, these are the best minimizing bras, if you’re into that. And here’s a roundup of bras for back pain relief.