Weatherstripping Calculator: measuring notes and method
Measure the actual seal path
An opening’s visible width and height may differ from the seal channel. Measure along the fitted seal route, and count each separate continuous seal once.
Check profile and corners
Length alone does not select the seal profile. Confirm corner joints, end treatments and whether each run must be continuous before converting the total into roll quantities.
Formula
Perimeter = 2 × (length + width) × number of openings. Apply waste.
Worked examples in metric and imperial units
Illustrative values match Reset example and stay fixed when you edit the calculator. Both columns describe the same calculation; converted inputs are rounded.
Metric worked example
- Length
- 6 m
- Width
- 4 m
- Quantity
- 1
- Waste allowance
- 10 %
Length including waste: 22 m
Imperial worked example
- Length
- 19.685 ft
- Width
- 13.1234 ft
- Quantity
- 1
- Waste allowance
- 10 %
Length including waste: 72.1785 ft
Follow the calculation
Lengths in this working are in metres.
- Net perimeter = 2 × (6 + 4) × 1 = 20 m.
- Allowance multiplier = 1 + 10 ÷ 100 = 1.1.
Reviewed 19 October 2026. How calculations are checked · Report a correction