Sweatpants have elastic waist, drawstring, pockets and are sized by the following waist chart and the maximum size they are available in is 3X:

Small = 28-30 inch waist
Medium = 32-34
Large = 36-38
XL = 40-42
XXL = 44-46
XXXL = 48-50

(please note this chart is only a guide to help you size, generally people buy the same size pants as they do shirt but it depends on how you like to wear your pants and remember this is an elastic waistline)