- 1). Wear a bra that fits you comfortably, even if you are not sure it is the right size. Make sure to choose a bra without padding, as padding can affect the accuracy of the measurement.
- 2). Use a tape measure to measure around your torso, placing the tape measure just under your breasts and noting the circumference around your rib cage and back. This can be done without removing clothing, although you should wear a thin T-shirt rather than a sweater if you don't want to remove your shirt.
- 3). Add about 5 inches to the number from Step 2. This is roughly your band size. If the number you got is odd, round up to the next size, since most bras are sold in even-numbered band sizes. Be sure to try on bras with the next size down and next size up to determine what works best.
- 4). Measure around the widest part of your breast, which is usually just under the nipple, for the number of inches all the way around your back. Be sure not to pull too firmly around the tape measure, as this can distort the accuracy of the measurement.
- 5). Subtract the number you received in Step 2 from the number you received in Step 4. The resulting number will give you an estimate of your cup size, with a difference of 1 inch being an "A" cup and then increasing a cup size for every inch over 1.
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