Quick answer

To measure for a wireless bra, wrap a soft tape snugly around your ribcage just under your bust for the band size, then measure around the fullest part of your bust for the cup size. Subtract the band measurement from the bust measurement: a 1-inch difference is an A cup, 2 inches is a B, 3 inches is a C, and so on. For wireless styles, prioritize a snug band and full-coverage cups, as the band provides most of the support.

Why wireless bras need a different measuring approach

Wireless bras rely on the band and cup construction for support, not an underwire. That means the band must be snug enough to stay in place without digging in, and the cups need to fully contain your breast tissue. If you measure the same way you would for an underwire bra, you might end up with a band that's too loose or cups that gap. Take your measurements while wearing a non-padded, unpadded bra or no bra at all, and stand in front of a mirror to keep the tape level.

What you'll need before you start

A soft measuring tape is essential; if you don't have one, use a string or ribbon and then measure it against a ruler. Wear a thin, unpadded bra or go braless. Have a pen and paper ready to jot down numbers. It also helps to know your current bra size as a reference, but don't let it bias your new measurements.

Step-by-step measuring guide

  1. Measure your band size: Wrap the tape around your ribcage, directly under your bust. Keep it snug and level. Round to the nearest whole inch. If the number is even, add 4 inches; if odd, add 5 inches to get your band size. For wireless bras, some brands use the exact underbust measurement as the band size, so check the brand's size chart. Common mistake: pulling the tape too loose. The band should feel secure but not restrictive.
  2. Measure your bust size: Wrap the tape around the fullest part of your bust, usually at nipple level. Keep the tape parallel to the floor and don't pull it tight. Round to the nearest whole inch. Checkpoint: the tape should touch your skin without compressing breast tissue.
  3. Calculate your cup size: Subtract your band measurement from your bust measurement. Each inch difference equals one cup size: 1 inch = A, 2 = B, 3 = C, 4 = D, 5 = DD/E, and so on. For wireless bras, if you're between cup sizes, choose the larger cup to avoid spillage. Common mistake: using an old band size. Always recalculate with fresh measurements.
  4. Try on and adjust: Use your new size as a starting point. Fasten the bra on the loosest hook and adjust straps so they stay put without digging. The band should be level all around and not ride up. Cups should lie flat against your chest without gaps or overflow. If the band rides up, go down a band size; if cups gap, go down a cup size.

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