Step 1: Ensure an accurate measurement (精确测量)
Wear your best fitting bra in order to get the most accurate measurement. Make sure the cups are not too small as this will give a smaller cup size than you require.
Step 2: Measure band size (测胸围)
Run a tape measure all the way around your body just underneath your breasts and take a measurement in inches. If the number is even, add 4 and if it is odd, add 5. This will give you your band size. For instance, if you measured 28 inches, your band size will be 32.
Step 3: Calculate cup size (测罩杯)
To find your cup size, measure around the fullest part of the bust in inches, not too tightly or the measurement will be inaccurate. Then subtract your band size from this measurement. This will help you to determine your cup size. If the bust size is less than the band size, you are an AA cup. If there is no difference between the two measurements, your cup size is A. A 1 inch difference indicates a B cup, 2 inches is a C cup, 3 is a D cup and so on. You can use this chart to find out your cup size.
minus 1 inches AA
0 inches A
1 inches B
2 inches C
3 inches D
4 inches DD
5 inches E
6 inches F
Now that you have a good idea of your true bra size, watch VideoJug's http://www.videojug.com/film/how-to-choose-a-well-fitting-bra for more advice on finding the right bra for you.