How to measure bra size: expert-backed tips for finding your perfect fit

When it comes to how to measure bra size, 'just like owning a car, there are things you are going to want to DIY and understand'

Close up of hands choosing bras cups size and looking light new wireless and seamless technology with red hot color and sexy bra in lingerie shop at department store. Woman shopping underwear concept.
(Image credit: Getty)

Confused about how to measure bra size? You're certainly not alone. Believe it or not, this art form has led many of us into unfamiliar and confounding territory.

There's no one way to get the gals in their respective cups perfectly, as we're all built so differently. Fortunately, there are ways to ensure maximum comfort and support, but you might need to ditch those age-old theories you've been conditioned to believe. 

If you're shopping for everyday bras or the best bralettes, we've asked an expert what to do when hopping in the fitting room. Kimmay Caldwell, the founder and "undergarment educator" of Hurray Kimmay, makes navigating this demi-cup dilemma a whole lot easier, and we're forever grateful. 

"The best and easiest way is to go to a professional. I think of bra fitters as really great mechanics," Caldwell says. "But just like owning a car, there are things you are going to want to DIY and understand."

Just like she teaches in her bra confidence and comfort course, there are five important notes to consider, and we'll take you through 'em all. Say goodbye to loose straps, uncomfortable underwires and all the stress that goes along with "boob cages."



How to measure bra size—Kimmay's five rules

Yes, it's totally possible to leave a store with both a 34D and 32C. Size doesn't necessarily matter, but Caldwell's five factors do.

"Kind of like jeans, you can measure for bra size—and there's a really basic formula that you can use to figure out where to start, but then they all fit differently," she notes. 

Above all, the bra has to form fit your body in order to function and keep you feeling comfy. Remember this golden rule!

Blue scallop bra hanging against white background

(Image credit: Getty Images)

1. The band

The band is the most important part of the bra and it quite literally does the heavy lifting. 

"[It's] 90% of the bras support," Caldwell says. "Ideally your bra should fit like a nice hug on your body and should stay in place and be parallel to the floor from right underneath your bust root to the back of your torso and around."

If you're going the traditional route with the three elastic hooks on the back, you'll want to start using the loosest fitting one but ensuring that it snug. 

"If it rides up because your breasts are pulling it down in the front, or if it rides up and your straps are now falling off, that band is too loose," she adds. 

2. The underwire 

Though not always ideal for some, underwire is a basic part of a typical bra. If you're going to have to snag a bra with one, make sure you know how to make it work best for you.

"You want that underwire to fit and flush against your body all the way around the breast," Caldwell says. "This sounds obvious, but you'd be surprised how many people have their underwires floating out from them. 

She adds: "Invite all of your bust inside the cup and then reassess: 'Can my underwire fit all the way around my bust and be flush on my body. Can everything fit inside?'"

3. The cup

It goes without saying, even if you're seeking a bit of a cleavage effect: there's no bubbling out and no spillage with a proper-fitting garment. 

"You don't want anything to be gapping or falling forward," Caldwell says. 

4. The straps

You might've been led to believe that the straps are doing the support, but this is just going to lead to indents in your shoulders and an uncomfortable day. Who needs that?

"Straps are only responsible for 10% of support," Caldwell says. "Their job is just to keep that cup fleshed to your body and provide a little extra support. Keeping the bra up is the band's job."

5. The feel

Everyone's body is so different, so it's important to be honest with how you feel, even if you end up with a different-sized brassiere than expected. Go with what feels right, keeps things in check and will be comfortable to wear throughout the day. 

Red flags to watch out for:

Caldwell notes that you'll want to avoid any bras that hike up your back as well as inexperienced fitters, as you wouldn't want an unknowledgeable mechanic playing around with your tools. 

Happy bra shopping, friends!