Sizing karate style belts works a bit different. Consult this chart to make sure you get the right fit:

size-inches-cm
00---72"---180
0---74.8"---187
1---84.4"---221
2---90.4"---226
3---98.6"---246.5
4---105.2"---263
5---114"---285
6---122.3"---306
7---131.4"---328.5

Just my input on this matter as a BJJ instructor for those interested in using these belts: the Tatami A3 BJJ white belts measure about 119 inches brand new. As I use the green belts in my adult BJJ belt system I am finding that the size 3 and size 4 Macho belts fit the average adult student pretty well. In BJJ the belts are thicker and should be worn down low on the hips/butt. If the belt is still too big have them wash and dry it. For kids you probably won't go much bigger than a size 2, with 00 thru 1 being the more common sizes you'll use. -oss