While braless or wearing a non-padded bra, use a measuring tape to measure around your torso directly under your bust, where a bra band would sit. The 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.)