Wearing a bra that does not fit correctly can lead to posture problems, back pain, and general discomfort, yet surveys show that many women regularly wear the wrong size bra. Determining the correct bra cup size for you is an easy procedure that can be done at home or by a trained sales clerk. To measure for bra cup size, you need a measuring tape from a sewing kit and some basic math. You will take two measurements, and when taking these measurements, you should be wearing the best fitting bra you currently own. It should not be a sports bra or minimizer bra, as this will result in measurements that are smaller than your actual size, nor should it be a padded bra or push-up bra, as this will lead to measurements larger than your actual size. Measurements tend to be most accurate when taken by someone else, so try to get a friend to help you.
Measure your band size first because you need this to figure out your bra cup size. Start by standing up straight and breathing as much air as possible out of your lungs. Then wrap the measuring tape around the band of the bra directly under the bust. Check that the tape is parallel to the floor to get the most accurate measurement.
Round the resulting number up or down to the nearest inch. Bra bands come in even-numbered sizes only, so if your rounded measurement is an odd number, add 5 to it. Otherwise add 4. For example, if your measuring tape reads 31.6, you would round up to 32 inches and then add 4. Your band size would be 36.
For the second measurement, stand straight with your arms at your sides. Wrap the tape measure around your back and over the largest part of your breast. Be sure the tape stays parallel to the floor. The tape measure should also be tight against the skin without squeezing. Round the resulting measurement up or down to the nearest inch.
With these two measurements, you will be able to determine your bra cup size. Take your band size and subtract it from the bra cup measurement. The difference between these two numbers is your cup size. If the difference is between half an inch and 1 inch, you are an A cup. If it is 2, your are a B, and so on.