We know, we know, maths was never our favourite school subject either. For argument's sake, let's say your cup measurement was 40 inches. The difference in inches equates to its respective letter ...

If you measure your band size as 34 inches and your cup size as 37 inches, the difference between the two is 3 inches. This means you have a C cup, and your bra size is 34C. And voilá!