Ordering the wrong zipper length or size is one of the most common — and most avoidable — sourcing errors. Whether you call it a zipper or a zip, measuring it correctly takes two minutes and saves a costly reorder. This guide shows you exactly what to measure and how to communicate it to a manufacturer.
Quick answer
To fully specify a zipper you need three things:
- Length — measured along the teeth, from stop to stop.
- Size (gauge) — the closed chain width: #3, #5, #8, etc.
- Type and ends — coil/metal/resin/waterproof, and open-end vs closed-end.
Give a supplier those three and you will get exactly what you expect.
What you are actually measuring
Two separate numbers often get confused:
- Length tells the manufacturer how long to cut the zipper.
- Size (gauge) tells them how wide and strong the chain is. (For the full breakdown of sizes, see our complete guide to zipper sizes.)
They are independent: a #5 zip can be 15 cm or 80 cm long. Always give both.
How to measure zipper length
- Close the zipper and lay it flat without stretching the tape.
- Measure along the teeth (the chain) — not the fabric tape extensions — from the top stop to the bottom stop.
- Record in cm or inches, and state which. For two-way and made-to-order zippers, give the exact stop-to-stop dimension.
- Tell the supplier whether your number is teeth-only or includes tape, to remove any ambiguity.
Measuring an existing zipper to reorder? Note the size stamped on the back of the slider too — it often shows the gauge.
How to identify zipper size
If you have a sample but no spec:
- Check the slider. Many sliders are stamped with the size (e.g. “5”, “8”) on the back.
- Measure the closed chain width in millimetres across the meshed teeth — roughly 5 mm means #5, 8 mm means #8.
- Compare the feel and use. Light apparel is usually #3; jackets and bags #5; heavy outerwear and luggage #8.
When in doubt, send the sample or a clear photo to your manufacturer.
Open-end vs closed-end
This changes how the zipper functions, so always specify it:
- Closed-end — joined at the bottom; used for pockets, cushions, dresses and bags.
- Open-end (separating) — fully separates; used for jacket and coat front closures.
- Two-way — opens from both ends; ideal for long coats, parkas and shells.
Common measuring mistakes
- Including the tape extensions in the length. Measure the teeth, stop to stop.
- Confusing length with size. They are different numbers — always give both.
- Stretching the tape while measuring. Lay it flat and relaxed.
- Forgetting the end type. A closed-end zip cannot replace an open-end jacket closure.
- Not stating units. Always say cm or inches.
The bottom line
Measure length along the teeth from stop to stop, identify the size from the slider stamp or chain width, and state the type and end style. Communicate all three clearly and your zippers will arrive right the first time. Still deciding between gauges? Compare #5 vs #8 or, for carry goods, see zipper sizes for bags and backpacks.
Have a sample to match? Send it to us with your length and we will confirm the size, type and slider and make a sample to approve.
Frequently asked questions
How do I measure zipper length? Close the zip, lay it flat, and measure along the teeth from the top stop to the bottom stop — not including the tape extensions. Record in cm or inches.
Where do I find the zipper size? Often stamped on the back of the slider (e.g. “5” or “8”). Otherwise, measure the closed chain width in millimetres: ~5 mm is #5, ~8 mm is #8.
Is zipper length measured with the tape or just the teeth? Standard practice is along the teeth, stop to stop. Always tell your supplier which method you used to avoid confusion.
What is the difference between an open-end and closed-end zip? A closed-end zip is joined at the bottom (pockets, dresses, bags); an open-end zip separates fully (jacket and coat fronts).
