Size Calculation – There's no standard way to determine belt sizes. I own two belts from different manufacturers that are ½" different in length. One is labeled 34 and one is 36. A person could fit perfectly at the first hole of a belt and then gain 30 lbs. and still fit comfortably at the last hole of the same belt. Therefore, we determine the size of the belt by measuring from the buckle end of belt leather to the center hole. That's the size we label the belt, but then we secretly add 2" to counter other factors (not a secret anymore).
So, if you wear a size 36 pant, then choose a 36 belt. It will be 38" from where the buckle attaches to the belt all the way to the center hole. We do this because we don't start the holes at 4" from the tip like most do, but rather at 2" (just in case) and also our holes are ¾" apart for comfortable adjustment instead of the 1" apart (too tight or too loose) standard. The belt could be a tad bit long on some, but it will probably fit just right like it does for me, at the center hole. If it's too long, no problem. Simply take out the 4 screws, slice off some of the belt and then put the buckle and screws back into the new holes already there. I made it so simple that my grandmother could do it.