Bra Fitting Encyclopedia

How to Measure Your Bra Size at Home

Take three underbust measurements and three bust measurements, average each set, and your band size is the average underbust rounded to the nearest even number. Your cup size is the difference between your average bust and that band, matched to a letter. Six numbers, one subtraction, one rounding. Or skip the tape entirely: the Radical scan takes two photos, front and side, and reads your measurements from them.

Measure without a tape: the two-photo scan

Radical measures through a Bodygram body scan: two photos, front and side, taken on your phone. No tape measure. Open fit.wearingradical.com, tie your hair up, wear a bralette, and set the phone on a counter at about waist height. The scan takes the two photos, reads them into your measurements and a 3D model of your body, and your pattern is drafted from those measurements plus a few questions, the same ones a certified fitter asks in person: what you wear now, what goes wrong, and where everything sits. It takes about two minutes.

Start your scan

Measuring with a soft tape

If you want the classic at-home method, here it is in full. You will need a soft, flexible measuring tape (not a rigid carpenter's tape), a mirror to check tape placement, and bare skin: remove your bra and any top for the most accurate measurements. Measuring without a bra matters because padded cups, underwires, and compression bands distort the numbers. If you cannot measure without a bra, wear an unpadded, non-minimizing one and expect slightly less accurate results.

Step 1: Measure your underbust (band size)

Take three underbust measurements, each at a different level of snugness, keeping the tape level and untwisted all the way around:

1. Comfortably snug. Wrap the tape firmly but comfortably under your breasts, standing upright and relaxed.
2. Tighter. Pull the tape tighter than the snug measurement, but still comfortably. This shows how compressible your ribcage is.
3. As tight as you can while breathing comfortably. This confirms whether your ribcage is firm or compressible, which affects band selection.

Average the three measurements and round the average to the nearest even number. An average of 31.25 inches rounds to a 32 band; an average of 35.0 is a 34 or 36 depending on the rounding convention you prefer.

Step 2: Measure your bust (cup size)

Take three bust measurements around the fullest part of your breasts, without pressing the tape into tissue:

1. Standing. Wrap the tape around the fullest part, usually at nipple height. If your fullness sits lower, measure at that lower point. If your breasts are different sizes, that is normal; just wrap the tape as usual.
2. Leaning forward 90 degrees. Bend at the waist so your breasts hang forward and measure around the fullest part. This captures tissue that standing misses, especially for pendulous breasts.
3. Lying flat. Lie on your back and measure around the fullest part. This redistributes tissue differently and gives a third data point.

Average the three.

Step 3: Calculate your size

Subtract your average underbust from your average bust. That difference is your cup difference; match it to a letter on the cup chart, then pair it with your band. A 32 band with a 4-inch difference is a 32D.

Fit accuracy tips

• If the tape slips down, it is too loose.
• If you cannot breathe comfortably, it is too tight.
• Use a mirror to keep the tape level, and keep it untwisted.
• Wrapping the tape around your back first, then bringing both ends together in front to read the number, is easier solo.

When measurements seem off

• Your bust measures smaller than your underbust. Common with smaller busts. The difference is zero or negative, which corresponds to an AA or A cup. Normal.
• Your leaning bust is much larger than your standing bust. Common with pendulous breasts; the leaning measurement captures tissue that hangs forward. Averaging accounts for it.
• Your three underbust numbers are very different. A wide gap means a compressible ribcage; a narrow gap means a firm one. Both are normal. See between sizes.
• Your result is far from your current size. Also common, and it does not mean either measurement is wrong. Many people wear the wrong size. Try the new size and judge by comfort.
• Your numbers change between sessions. Small differences in tape placement or posture can change a measurement by half an inch or more. Re-measure.