http://www.85b.org/bra_calc.php
Try this one. It takes measurements in cm and inches. And it shows you where to measure.
Although, I would recommend getting a shop to measure you, as they will also allow you to try on different styles and sizes until you find one you are completely comfortable with!
Take a friend along, and tell the shop assistant you don't like getting it done as someone was incredibly rude to you in the past!! I would imagine they'd be very understanding.
Good luck!!
ERx