Buying and Measuring a Zipper
Zippers come in a wide variety of lengths but they are not always the perfect length for what you want to create or for what you are sewing. It is rare for ready-made garments to have the same size zipper that would match what is available for home sewing. Shortening a zipper for it to fit is not a hard task.
Shortening a zipper does not mean you have to have zipper teeth poking into your skin on garments.
Always a buy a zipper that is longer than you need if the perfect length is not available.
Measure and Bar Tack the Zipper
Measure the area you want to insert the zipper into.
Transfer the measurement on to the zipper and mark the zipper tape for the length you want.
Sew a bar tack over the zipper teeth at the mark. A bar tack is sewn by setting the stitch width wide enough for the needle to land on both sides of the zipper teeth and setting the stitch length so that the stitches are almost right on top of each other.
Cutting and Removing Zipper Teeth
Cut the zipper below the bar tack, leaving 3/4 inch to 1 inch of zipper.
Carefully snip just the teeth off of the zipper tape, leaving as much of the zipper tape intact as possible.
Backing the Cut End
Place a ribbon, scrap of bias tape or fabric on the back side of the zipper under where you removed the teeth. This backing fabric will give you a smooth surface to keep the zipper tape intact and protect your skin.
Finishing a Shortened Zipper
Zigzag over the edges of the zipper tape and backing material, keeping the edges of the zipper tape even with the original zipper tape width as well as flat and smooth. Zigzag the raw end of the zipper tape to prevent fraying.
Sew the zipper in as you normally would.