How a women actually determine their bra size?

Have a look on this video click. You May find something.

Find more on basic step to determine the bra size.
Knowing Your Bra Size?

Actually the Brassiere size is determined by the size of the underbust and the cup size is by the size of the area between the top bust and underbust.

Find the following 3 basic step on how to go about determining your bra size.
Step 1: Measure your under bust
Step 2: Measure your overbust & take the difference over your underbust
Step 3: Match again the size in the chart below

The Underbust in between          Look For Body Size

68 – 72cm                                               70                        
73 – 77cm                                               75
78 – 82cm                                               80
83 – 87cm                                               85
88 – 92cm                                               90

Different Between underhust & Overhust                    Look For Cup Size

10 – 12cm                                                                                     A
13 – 14cm                                                                                     B
15 – 17cm                                                                                     C
18 – 19cm                                                                                     D
20 – 21cm                                                                                     E
> 22cm                                                                                         F