To ensure you order the right size, we strongly encourage you to measure your waist (or hips, depending on how you prefer to wear your belt).
Unisex Sizing: S = 27-29, M = 30-32, L = 33-35, XL = 36-38
The length of the belt matches the smaller end of the size. For example, a Medium (30-32) measures 30 inches around. When the bottles of the belt are full, the added weight creates more stretch, expanding the belt. The Velcro closure allows you to adjust the belt a couple inches to create the perfect fit. For men - Keep in mind these are unisex sizes. Men who usually wear a Mens Medium are usually a unisex Large. Measure your waist to be sure. For women Keep in mind these measurements are for your natural waist, which is much higher than where most women wear their pants these days. If you like to wear your Fuel Belt lower on your waist or hips, measure that area accordingly. (Typically it means you have to go up a size.)