To obtain the correct belt size, take a tailor's tape and measure around your waist. For women, measure your waist and add 3 inches to determine your belt size. For instance, if your waist measures 27 inches, you should order a belt size of 30. For men, measure your waist and add 2 inches to determine your belt size. For example, if your waist measures 38 inches, you should order a belt size of 40.