The size of the garment is determined by the number of inches from the shoulder seam to the end of the sleeve. The size of a garment is determined by two measurements: bust and waist. The bust measurement is taken around the fullest part of your chest, while the waist measurement is taken at your natural waistline, which should be above your belly button. If you're wearing a dress with a fitted bodice, measure it where it will fit best on you.