When it comes to apparel, it’s the foundational pieces that are the most critical to our overall wardrobes and looks. However, these are often the very pieces that can be the most difficult to get right in terms of fit, form, and function, with one item proving to be particularly tricky for women: the bra. While finding a properly fitting undergarment can have a major impact on how the rest of our clothing looks, many women don’t even know their true bra size. To help demystify the process of finding the perfect bra, we reached out to Kelly Rocha, owner of Truly U Bras in Omaha, Nebraska, for expert advice. Here are her recommendations.

Get offline, and go to a local bra boutique. “There are no standards for cup or band size, so every brand is different,” Rocha explains. This means that the best way to find a bra that fits is to go to a local store that has certified bra fitters who can take proper measurements (see below for more on this) and try on different options. Be prepared to walk out with several different sizes, as sizing will vary depending on the brand and style of bra—which makes buying online all the more risky.

Trust the experts. The only way to ensure you are wearing the correct size is to be fitted by a certified bra fitter—preferably someone with years of experience. “Being able to fit each client with the right bra is so much more than taking measurements,” Rocha says. “Certified fitters have experience with each brand and different body types, so they will be able to make the best recommendation for your unique figure. It truly is a science that takes years to master.” Here’s what they’re looking for:

  • Band size. To get a general idea of sizing, your fit specialist will start by measuring right under the base of the breasts, parallel around your body. This measurement will give you your band size. Rocha notes this is difficult to do alone, as it’s hard to ensure that the tape is straight.
  • Cup size. The second measurement your specialist will take is of the circumference of the breast tissue and rib cage, so the tape measure goes around your chest wall, including the bustiest portion of your breast. Your specialist will take this measurement and subtract it from the first measurement to get a number that translates into your cup size.

Know what constitutes the correct fit. Of course, you want your undergarments to be comfortable, and you probably have a general sense of whether or not a bra is the right size when you put it on, but what truly makes for a perfect fit? Here, Rocha outlines the key criteria, and how to optimize your wearing experience.

  • Find a snug band. This is the most important factor, according to Rocha. What you’re looking for here is a band that rests snugly against the chest wall. “A good test is to lift up your arms. If your bra moves, you need to tighten your clips or get a snugger bra around the chest wall,” Rocha advises, adding that going down a band size usually does the trick. In addition, the band is the part of the bra that holds up the weight of the breast tissue, so if you’re having issues with sagging, that’s a sign your bra is too loose.
  • Pay attention to the center panel. You want your garment’s gore (the part in the center that connects the cups) to lie flat against your chest. If it begins to float, Rocha says this is an indicator that either your cup is too small, your band is too big, or possibly both.
  • Remember to swoop and scoop. This motion is key to a proper fit, Rocha says. Simply grab your breast from the side of the cup near your armpit and slightly bring it forward while tucking your underwire gently back. This ensures your breast will be firmly in the cup of the bra, which not only makes the bra more comfortable for all-day wear, but also protects your lymphatic system.
  • Only fasten on the loosest hook. You should always purchase a bra that fits on at least the first two rows of hooks from the end, Rocha says. Begin by fastening the bra on the outermost hook, and as the bra stretches—and it will—you can start progressively using the clips further in for continued proper fit and support.
  • Expect it to feel snug at first. “Many women go up in their band size instead of breaking in a bra,” Rocha says, “which only lessens the life of the bra and compromises your support.” She shares this test to determine if the band is the right fit for you: When you pull on the band, you should be able to fit a golf ball between the band and your back. “In order to have the support in the rib cage, the band of the bra needs to be snug like a hug, not tight like you want to burn the bra at the end of the night,” she says. After five wears the bra should feel comfortable and like a second skin.

Photography by The Mullers. TSG Tip 349 from Kelly Rocha, owner of Truly U Bras in Omaha, Nebraska. Truly U is featured in The Scout Guide Omaha.