You need two measurements to calculate your bra size: band and cup. Use a tailor’s tape measure to take these measurements. Keep the tape parallel to the floor, do not pull it tight, and measure against the skin for the most accurate results. UK bra sizes are calculated in inches, so it is best to take the measurement in inches or to convert metric measurements to imperial units.
To obtain your band measurement, expel all the air from your lungs while you measure. Run the tape around your torso, directly under your bra. Round off all fractions to the nearest whole number. Remember that fractions under a half are rounded down, while fractions of a half or more are rounded up. For example, 32.4 is rounded down to 32, while 32.5 is rounded up to 33. Use the table below to find your band size.
Band sizes over 38 are equal to the whole even number closest to the bra band measurement. For example, a measurement of 43 inches equates to a 44 band size.
Bust size can be measured while you are wearing a bra, provided the bra is not padded. You may need to ask a friend or family member for help. This measurement should be taken while you stand up straight with your arms at your sides. Measure across the fullest part of your bust. Do not pull the tape measure tight and keep it parallel to the floor. Round the measurement to the nearest whole number.
To calculate your bra cup size, subtract your band size from your bust measurement. For example, if your band size measurement is 30 inches, then your band measurement is 32 from the table above. So, if your bust measurement is 34 inches, then your bra cup size is equal to 34 minus 32, which is equal to 2. Use this number and the table below to find your corresponding alphabetical cup size. In this case, the cup size would be B. Therefore, the bra size would be a 32B.
Band Minus Bust Difference
US Cup Sizes
|Less than 1"||AA||AA||AA|