Zipper Length Calculator
Choose a zipper length for a garment, bag or cushion from the opening length and seam allowance.
Compare Your Options And Get Clear Answers
Choose a zipper length for a garment, bag or cushion from the opening length and seam allowance.
Zipper Length Estimator
Enter your numbers below for an instant estimate.
How It Works
Key concepts behind this calculator
Enter Values
Fill in each field with your own numbers.
Calculate
Results update as you change the inputs.
Review
Read the breakdown and the explanation.
Adjust
Change values to compare scenarios.
Zipper Quick Guide
Typical values for reference.
| Opening cm | Type | Seam cm | Zip cm |
|---|---|---|---|
| 12 | 2 | 1.5 | 12 cm |
| 25 | 2 | 1.5 | 25 cm |
| 45 | 1 | 1.5 | 50 cm |
| 70 | 3 | 1.5 | 70 cm |
| Rule of Thumb | Check inputs | Use as a guide | Round sensibly |
Zipper Length Calculator FAQ
Answers to common questions about this calculator.
About 5 cm shorter than the back opening, plus seam allowance.
Yes for coil zips, metal zips are harder.
Zipper length = opening length (+ 2 cm for invisible) rounded to a standard size.
It is an estimate based on the inputs you enter. Check real quotes, labels or official guidance for important decisions.