While braless or wearing a non-padded bra, take a measuring tape and measure snugly around your torso, directly under your bust at your rib cage. Make sure the measuring tape is straight and level, and lays flat across your back. When noting the measurement, round to the nearest whole inch. If the rounded number is an even number, add four inches. If the rounded measurement is an odd number, add five inches. (For example, 32 plus 4 equals 36 inches or 29 plus 5 equals 34 inches.) This final calculated sum is your band size.

Band sizes come in even numbers 32, 34, 36, etc., but if you feel that you are between two sizes after calculating your band, let’s say a 33, you should try on both a 32 and 34. Depending on the brand, one size should fit better than the other. Or, for the most perfect custom fit, you can just buy the bigger band size and have a tailor take in the band for you as a relatively inexpensive fix.