Bra size

Measurement 1: Place a tape measure across the bust, just below the chest (with the tape measure tight).
Measurement 2: Wrap a tape measure around your chest (with tape measure loose).

Underwear size

Measurement 1: Measure around your waist (the thinnest part of your torso).
Measurement 2: Measure around the hips (the widest part of the buttocks).