Measuring for Bras.
One extra hint that I learned at Rigby and Peller (heaven on earth as far as bra shopping goes).
If you want a decent fit, after you measure around the rib cage, take two inches off. That way you get a bra that fits comfortably on the outside hook when you buy it, and can be adjusted as it stretches.
R&P by the way keep bras in stock in sizes you wouldn't believe: 52C anyone?