Window maintenance
Window Seal Replacement Length Calculator
Estimate the replacement seal or gasket length required for rectangular windows. Choose the seal path, enter frame dimensions and add an explicit allowance for cuts, corners and joining.
Replacement seal inputs
Replacement seal profiles differ in geometry, stretch behavior, joint requirements and retention method. This tool estimates linear material quantity and does not identify the correct seal profile.
Replacement seal requirement
Planning seal length
—
For all selected windows
—Per window
—Net length
—Allowance
—Windows
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Seal-length formula
Four-sided = 2 × (width + height)
Three-sided = 2 × height + width
Planning quantity = net length × (1 + allowance ÷ 100)
Three-sided = 2 × height + width
Planning quantity = net length × (1 + allowance ÷ 100)
Measure the actual seal path
Before ordering replacement gasket, identify where the seal sits in the frame. A glazing gasket, compression seal and weatherstrip can follow different paths.
Why an allowance helps
Old seal removal, corner cuts and replacement joints can make installed material differ from a theoretical perimeter. Keep the allowance explicit so it is easy to adjust after measuring one sample window.
Worked example
Eight windows measure 1.2 m × 1.5 m and use a four-sided replacement seal:
Per window = 2 × (1.2 + 1.5) = 5.4 m
Net = 5.4 × 8 = 43.2 m
With 8% allowance = 46.656 m
Net = 5.4 × 8 = 43.2 m
With 8% allowance = 46.656 m
Frequently Asked Questions
Does this identify the correct gasket?
No.
Can I use three-sided seals?
Yes.
Should I add a replacement allowance?
Usually an explicit project allowance is useful where cutting and corner losses are expected.
Does it calculate seal compression?
No.