In the Netherlands the size of the ribcage is the same as the number on the bra. The difference between the size of the ribcage and the breast size determines your cup size. If around your ribcage beneath your breasts you measure 75 cm. and across your breasts you measure 88 cm, you can best try 75A.

Difference
in cm:                  cupsize
10-12                    AA
12-14                    A
14-16                    B
16-18                    C
18-20                    D
20-22                    E (DD)
22-24                    F
24-26                    G

In England you measure beneath your breasts and then add 5 inches to an odd number and 4 inches to an even number. Then you measure across your breasts. The difference in inches determines your cup size.

Rib cage     Bra size     Difference             Cupsize
                                      in inches
25-26              30                    5                      A
27-28              32                    6                      B
29-30              34                    7                      C
31-32              36                    8                      D
33-34              38                    9                      DD
35-36              40                    10                    E
37-38              42                    11                    F
39-40              44                    12                    FF
41-42              46                    13                    G
43-44              48                    14                    GG
45-46              50                    15                    H