If there’s anything more frustrating than trying on jeans, it’s trying on bras. At least when it comes to denim, you can pretty much decode your size from one brand to the next based on your measurements. But for whatever reason, finding the perfect bra for your bust — specifically regarding strapless styles — is a trickier task.

While bra sizes are based on measurements, too, it can be hard to tell if your strapless bra fits correctly. This is because a lack of straps eliminates a key source of support and security, and therefore increases the odds of your bra either slipping down throughout the day or gaping in the front. To help you find the right fit for your strapless bra, we tapped experts to share their tips and tricks.

Get Fitted

Getting fitted for a strapless bra is key, says stylist and fashion writer Samantha Sutton. “Much like pants, tops, and dresses, some [strapless bras] may look great on you, while others will seem less than flattering,” Sutton says. “It will take a bit of trial and error to find a specific strapless design that suits you and your body.”

But before you commit, expert bra fitter, Annette Bourne says there’s a vetting process that needs to take place. Getting measured is just the first step; you have to try on some strapless bras and get a feel for different styles in terms of comfortability and support.

Assess Different Styles

When a strapless bra fits well, “the band sitting along your rib cage will feel secure enough that it will sit on the body and not slide off [while you’re wearing it],” Bourne tells InStyle. “It should lift the breasts in such a way that the top of the breasts should not be bubbling over the top of the bra (unless it's a push-up bra.”

If you have a bigger cup size, you may also want to consider a wider style band, says fashion stylist and style expert, Naina Singla. And if you’re having trouble keeping your strapless bra in place, consider sizing down a band “to keep the bra snug, so you can move freely.”

Test It Out

And as for determining if your strapless bra will stay in place throughout the day, Bourne has a few fool-proof methods. First, she recommends pulling up from the top of the bra and taking note of whether or not your breasts slide out from the bottom of the bra. Second, take note of what’s going on in the back. A good-fitting strapless bra won’t “slip or slide” on your back, Bourne stresses. Lastly, Bourne says, if a strapless bra fits correctly, “The bosom will sit midway between the shoulder and elbow from the side profile,” and the breasts will be separated.

But here’s the catch: Your bra should be just as supportive for your breasts when you move as it is when you’re standing still. To test this, Sutton recommends that before you leave the dressing room you, “raise your arms above your head, do a bit of wiggling, and jump around,” to ensure the garment stays in place. Sutton also suggests either wearing or bringing a top you’d wear with a strapless bra to the store, so you can see how the styles you’re considering sit under your actual clothes. “The goal is for your bra to look smooth underneath your clothes, so if you notice any weird lumps and bumps, it probably isn’t the right size or [style].”

Together, these details will ensure your breasts will stay supported and securely in place throughout the day, and that your dress or shirt will lay seamlessly on the body.

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