Size guide.

Men

Size Jeans Waist
XS 28 26-28 inch
S 29 28-30 inch
M 30/31 30-32 inch
L 32/33 32-34 inch
XL 34/36 34-36 inch
XXL 38/40 36-38 inch
3XL 42 38-40 inch

Boys

Size Age
104 3-4
110-116 5-6
122-128 7-8
134-140 9-10
146-152 11-12