How To Measure Bra Size Dear BeingGirl Experts, There are so many types of bras. Sports, extra padding, and so many sizes!! Once I was shopping with my sister and there was a bra with water in it! Onto my question: how do I measure to find the size bra that I need? Your help is appreciated. Thanks, Beth --- Dear Beth, The first measurement you take is around your chest, just below your breasts. Next you will want to find out what cup you need. Measure around the fullest part of your breasts and... If the two numbers are the same, you need an AA-cup. If the two numbers differ by 1 inch, you need an A-cup. If the two numbers differ by 2 inches, you need a B-cup. If the two numbers differ by 3 inches, you need a C-cup. If the two numbers differ by 4 inches, you need a D-cup. Remember this is just a guide. You really need to try bras on and find the one that fits best. When buying a new bra make sure it hooks comfortably on the last hook so that as it stretches you will still be able to hook it. Buy one bra and wear it to be sure that the bra is right for you. Hope this is helpful, Your BeingGirl Experts Find out how to measure bra size with expert advice and tips from BeingGirl.