How to Measure Your Bra Size

Wearing the wrong bra size can ruin an otherwise flawless outfit. These step-by-step measuring instructions will ensure a perfect fit.

Are you wearing the right size?

Here are a few telltale signs that you may not be: wrinkling in the cups, underwire poking the sides of your breasts, a band that rides up, cup spillage, slipping straps, or a bra that hikes up when you lift your arms, says Sandi Simon, a fit consultant at Bra Smyth, in New York City. (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.) 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.

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Step 1: Determine your band size

While braless or wearing a non-padded bra, measure around the bottom of the band, directly under your bust. The measuring tape should be level and very snug. Round to the nearest whole number. If the number is even, add four inches. If it’s odd, add five. Your band size is the sum of this calculation. (So if you measured 32 inches, your band size is 36. If you measured 33 inches, your band size is 38.)

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Step 2: Take your bust measurement

Wrap the measuring tape somewhat loosely around the fullest part of your chest (at nipple level). Round to the nearest whole number.

Step 3: Calculate your cup size

Subtract your band size from your bust measurement and refer to chart. Example: 37 inches (bust) – 34 inches (band) = 3 inches. That’s a 34C.

So how can you tell if a particular style fits? Try these tips:

Bend forward at the waist, then slip on the bra and hook it. This ensures your breasts are completely in the cups.

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Adjust the band. The back of the bra should be level with the front.

Make sure the bra is not too loose. You should be able to slide only one finger underneath the band.

Fix falling straps. First, tighten the band, then shorten the straps.

Put on a close-fitting shirt over the bra. If the cups pucker or your breasts bulge, you’re not wearing the correct size.

Look at yourself sideways in a mirror. Your breasts should sit midway between your shoulders and elbows. If not, you need a more supportive and better-fitting bra.

If you need to go down a cup size for fit, go up one band size, and vice versa. For example, if a 34C is too big for you, move to a 36B.

Choose a bra that fits perfectly when secured on the outermost hook. As the bra loosens over time, make the band taut by moving toward the tightest hook.

This article originally appeared on RealSimple.com