To make the pattern, fold your pants in half and pull the crotch all the way out. Flatten them as much as possible and lay them down on top of your paper. Parchment paper is inexpensive and wide enough for most childrens sizes. I like regular rolled wrapping paper for adult pants since it's wide enough and it's cheap. Trace around the pants. If your pants have a drawstring or elastic, make sure you trace them with the waist stretched completely out. Add a seam allowance by drawing an outline 1 / 2 inch outside the traced lines along the legs and crotch and 2 inches along the waist and hem of the pants. Put the pants aside and cut your pattern out.