The manufacturer recommends to go with the size that is closest to your measured waist size but does not exceed your waist size.
Below is the measurements for each belt:
Med - 33 1/2"
Large - 36 1/2"
XL - 40"
XXL - 43"
If you need further assistance in which size to choose, please reach out to the manufacturer directly at: Lamb@VikingTactics.com