Zipper Length Calculator
Match your opening to the nearest standard zipper length for garments, pillows, cushions and bags.
How it works
Target = opening + project adjustment (garment 0 · bag −1 · pillow −2 · cushion −3 in) · Recommended = nearest stocked standard length (pillows/cushions round down)
Zippers are sold in fixed lengths — 7, 9, 12, 14, 22 inches and so on — so the job is matching your opening to the closest stocked size. Garments use a zipper the same length as the opening, while pillow and cushion covers use one an inch or two shorter so the seamed corners tuck over the metal stops and hide them. This tool applies the right project adjustment and then snaps to the nearest standard length.
Worked example
A 20 in pillow opening takes a target of 20 − 2 = 18 in. The nearest stocked size at or below that is exactly 18 in, so an 18 in zipper leaves an inch of seam at each corner to conceal the ends.
Frequently asked questions
Why use a shorter zipper on a pillow than the opening?
A zipper a couple of inches shorter lets you sew the seam past both ends, so the corners fold over and hide the metal stops. A full-length zipper would run right into the corners and be awkward to finish neatly.
Can I shorten a zipper that is too long?
Yes. Nylon coil zippers shorten easily: mark the new length, stitch a bar tack across the coils as a new stop, and cut off the excess below it. That means you can safely buy the next size up when your exact length is not stocked.
What length zipper for an invisible dress zipper?
Match the finished opening or go slightly longer — invisible zippers are measured to the pull, and having a little extra above the seam makes them easier to insert before you trim. Choose the garment option for a same-length recommendation.
Related calculators
This calculator is for educational purposes. Double-check important results before acting on them.