You must measure your waist at the navel. Order your corset in a size that is 4" to 6" below that measurement. For example, if your waist size is a 40 order a size 34 or 36 corset. If you have a bit of a belly, or have never worn a corset before order 4" below your waist size. If you are thin, or already have some corset training, order 6" below your waist size. They are sold in standard waist sizes 18" - 38", accommodating customers up to 4X. Corsets are to be ordered 4 inches below the natural waist measurement. Those with natural waists of 34 inches or more can typically order 4" - 6" below the natural waist. These customers are usually softer in the middle and have more "cinching" capability. Otherwise, you risk getting a corset that laces completely closed, not offering any cinching-in capability, and being too loose. We also wish to remind you that your "natural waist" refers to the narrowest part of your waist directly under the ribcage (and not the lower belly).