Bra size is notoriously fickle between different lingerie brands; a C-cup at one store can easily be a D-cup at another, and some bra sizes can grow and shrink (especially in band size) over the course of a day or between washings. The best option is to know your bra size by taking bust measurements using these simple measuring instructions, which will ensure a perfect fit in band and in cup—and can even help you find the right amount of support. Learning how to measure bra size can feel uncomfortable, but knowing your measurements—and keeping them written in a note on your phone or somewhere else that’s accessible when the bra-shopping mood strikes—will make bra shopping so much easier, especially for online shoppers. Equipment for measuring bra size is minimal: All you need is a tape measure and a little free time, and you’ll have saved yourself a lot of bra-shopping misery. Best of all, knowing how to measure your bust will make adjusting to changes in your breasts (from losing or gaining weight, hormone fluctuations, aging, pregnancy, and more) so much less stressful. Bra size shouldn’t be a guessing game. With this guide, managing irregular bra cup sizes (yes, even for sports bras) should be a breeze, and sore, achy breasts from ill-fitting bras will be a thing of the past.

Wrinkling in the cupsUnderwire poking the sides of your breastsA band that rides upCup spillageSlipping strapsBra that hikes up when you lift your arms

If you suffer from any of the fit issues above, head to a professional bra fitter—or bust out the measuring tape and follow the steps here to measure your bra size at home. (But keep in mind that certain factors can cause you to change bra size—a weight gain or loss, a new exercise regimen, pregnancy, and a change of diet among them.)

Why do my bra straps keep falling down?

Cohen explains that your bra straps are likely falling down for one of two reasons: “I recommend purchasing a new bra every six months to a year, depending on how often you wear it, to ensure you have the best, most flattering fit,” Cohen says.

What are the best types of bras for my shape?

Whether your breasts are asymmetric, large or small, round or slender, or somewhere in between, there are bras out there that can fit your unique shape. It’s just a matter of finding the best bra for your shape. Cohen recommends the best fitting bras for six common breast shapes.

Asymmetric: If your breasts are different sizes, you’re not alone—around 40 percent of women who experience ThirdLove’s Virtual Fitting Room classify themselves as having this breast shape, Cohen says. She recommends a bra that has removable inserts, so you can incorporate an insert on one side to give your smaller breast a boost.Athletic: Wider breasts with more muscle and less tissue tend to have a problem with cup gaping. Due to this, Cohen recommends t-shirt style bras.East West: These are wide-set breasts that have nipples that point to the east and west, just as the name suggests. If you are struggling to achieve cleavage with certain tops, look for full-coverage bras that will help bring your breasts up and together.Bell Shaped: These breasts are slimmer at the top and fuller at the bottom. This normally characterizes someone as a larger cup size and they may experience overflow with minimal coverage styles like balconette or demi. Instead, try a full-coverage bra that features wider memory foam straps that provide support, but don’t dig in.Relaxed: These are breasts that have lax tissue, and nipples pointing downward. Since these tend to be longer breasts that hang, try a balconette style bra that has a slightly shorter cup for more fullness at the top.Round: While most styles may work for your shape, try a wireless bra for days when you want light support or balconette style when you want an ultra-flattering fit.

How do you measure bra size without a measuring tape?

If you don’t have a measuring tape on-hand, you can still measure your bra size at home. ThirdLove shares an easy two-step method: If you don’t have any of these tools available, ThirdLove also has a virtual Fitting Room using expert bra fitting knowledge and data points from millions of real customers.