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How to find the zipper size
- Check the back of the slider, where the size is often stamped.
- Close the zipper.
- Measure the width of the interlocked teeth in millimetres.
- Round to the nearest standard size and confirm with the manufacturer.
The number on a slider does not always show its size, so do not rely on it alone.
How to measure length
- Closed-end: Usually from the slider top to the end of the bottom stop.
- Open-end: Usually from the slider top to the end of the box.
Some manufacturers start from the top stop. Allow for the tape extensions too, and state your measuring points when ordering.
What is the tolerance?
Small length differences are normal. Tolerances grow with length, from a few millimetres on short zippers to a few centimetres on long ones. Ask for the manufacturer's figures on precise jobs.
Identifying the type
Separate metal teeth mean metal, separate plastic teeth mean molded plastic, and a continuous spiral means coil.
Measuring the size, step by step
- Close the zipper fully.
- Place the ruler across the teeth.
- Read the widest point of the closed teeth in millimetres; do not count the tape.
- Round to the nearest standard size.
- Check the number on the back of the slider too, but do not rely on it alone. It can be a mould number.
| Width you measured (approx.) | Likely class |
|---|---|
| 4.0-5.5 mm | Light (Size 3-4) |
| 5.5-7.0 mm | Medium (Size 5) |
| 7.0-8.5 mm | Medium-heavy (Size 8) |
| 8.5-12 mm | Heavy (Size 10) |
The ranges are based on JIS classes; small differences occur by maker and chain type. See the size guide for details. To match an old zipper, send us the measurements with a sample request.
