You need to know your height, weight, and shoe size (for bootfoot waders). Also factor in the clothing you intend to wear under the waders, whether that’s a T-shirt and shorts or a thick sweater and long underwear. In stocking feet, measure your inseam from floor to crotch. Then measure around the biggest part of your body (chest, waist, or hips) for the maximum girth. Compare your measurements to the sizing chart for that particular brand of waders.