A zipper is an inexpensive part of a piece of clothing, but when a zipper breaks, it renders a garment unwearable. Seamstresses can give your apparel a second chance by replacing broken zippers for a fee. Those who are savvy with a needle and thread can replace zippers with minimal effort. But not all zippers are the same. Determine the defective zipper's size and replace with another of the same size.
Flip back the zipper's slide and look for a number. This number is usually the size of the zipper.
Measure the width of the zipper's teeth in millimeters after the zipper is closed, if there is no number on the slide. Use this measurement for the zipper's size. If the teeth are five millimeters wide, then the zipper is a size five.
Measure the length of the zipper in inches or centimeters from the stop at the top of the zipper to the stop at the bottom of the zipper. Find replacement zippers sorted by type, length and color at any store that carries sewing supplies.