Women's trousers are usually measured differently than men's trousers. Although some manufacturers do use similar measurements, most will size women's trousers based on a number that corresponds to the size of a woman's waist, and occasionally her hips. Knowing your correct size is especially helpful when you do not have the luxury of trying on the trousers before purchasing them.
Measure around your waist at the narrowest area, usually around your belly button.
Measure the distance around your hips at the base of your hip bone.
Reference your size based on a size chart. Normally, this is referenced by waist measurement, but if your hips are larger than the size allows, then you may opt to use the hip measurement to determine size. As an example, size "2" is used for a 24.5-inch waist or 35.5-inch hips. Size "10" refers to a 28.5-inch waist or 40-inch hips.
Reference standard sizes, such as "small," "medium" or "large," based on waist size. As an example, size "small" relates to waist measurements of 26.5 inches to 27.5 inches, or numerical sizes "6" to "8."
Measure the length from the base of your hip bone to the base of your ankle bone. Combine this with your waist measurement, such as 28 inches by 32 inches, related to waist and inseam measurements, respectively.