I ordered my usual belt size for suit belts and other golf belts I have and it turned out to be a little big as the end was dangling a bit from the belt loop. I would recommend going 1-2 sizes down, especially since the strap is stretchy.
Pros
Pants 38 inches. xml was too big, had to scale down. A size smaller belt was perfect. Like it a lot
Cons
Limited Size Options: Although the belt comes in a variety of sizes, some users may not find their perfect size due to the limited size options.