In terms of quantity, a zip of weed is used to describe 28 grams of cannabis. Or, in mathematical terms, 1 zip of weed equals 28 grams. This is a pretty big pile of cannabis. In terms of rolls or joints, a zip of cannabis contains 40 joints of cannabis. This is obtained by a practical breakdown of how much cannabis an average joint contains, which is 0.7 grams. (Note that this is an estimate), your joint could sometimes be heavier or lighter than this amount.