Measure under your breasts, snug but not tight, keep the tape measure level all the way around.

24.5 – 26.5 in = 32
26.5 – 28.5 in = 32
28.5 – 30.5 in = 34
30.5 – 32.5 in = 36
32.5 – 34.5 in = 38
34.5 – 36.5 in = 40
36.5 – 38.5 in = 42
38.5 – 40.5 in = 44
40.5 – 42.5 in = 46

Measure under your fullest part of breasts, not too tightly, and press down between them.

Subtract Measurement 1 from Measurement 2.

1.5 – 2.5 in → A
2.5 – 3.5 in → B
3.5 – 4.5 in → C
4.5 – 5.5 in → D
5.5 – 6.5 in → DD / E
6.5 – 7.5 in → DDD / F
7.5 – 8.5 in → G
8.5 – 9.5 in → H