Floors & Walls
Siding Calculator
Estimate siding cartons from wall area, openings, waste and effective coverage.
Enter your measurements
Results update as you type.
About this calculator
Enter rectangular or gable (triangular) wall sections, subtract window and door openings, add waste, and divide by the manufacturer's effective coverage per carton or panel — effective coverage already accounts for overlap, so no second deduction is made.
How to use this calculator
- Measure each wall section; run gables as triangular sections.
- Subtract the total area of windows and doors.
- Use the manufacturer's effective coverage, which already includes overlap.
- Calculate for whole cartons, panels or squares.
Formula
Net area = wall sections − openings
Order area = net area × (1 + waste ÷ 100)
Units = ⌈order area ÷ effective coverage⌉
Assumptions
- Effective coverage is used, not nominal panel dimensions — overlap is already accounted for.
- Waste is applied once to the net area.
- Openings larger than the gross wall area are rejected.
Common mistakes
- Counting excluded or overlapping areas twice.
- Using nominal dimensions where actual installed dimensions or usable coverage are needed.
- Treating whole purchase quantities as an optimized cutting or installation plan.
Worked example
Try it: press “Load example” above the form.
1000 ft² less 100 ft² of openings is 900 ft² net; with 10% waste, 990 ft², so 5 cartons at 200 ft² each.
Limitations
No fastener spacing, wind-load, flashing or installation-code prescriptions.
Frequently asked questions
Can I subtract doors and windows?
Enter their area as openings on the same measurement basis as the gross wall area. Large cuts and trim details can still create waste, so do not assume every offcut is reusable.
Does panel area equal installed coverage?
Not always. Lap, reveal and product overlap reduce useful coverage. Use the installed coverage or carton figure from the selected product.
What does the worked example show?
1000 ft² less 100 ft² of openings is 900 ft² net; with 10% waste, 990 ft², so 5 cartons at 200 ft² each.
Which assumptions should I check before using the result?
No fastener spacing, wind-load, flashing or installation-code prescriptions.
Sources
Sources explain the methods and any named product presets. Check your product label where coverage, yield or density differs.
Calculation documentation · Updated 2026-11-08 · Version 1.6.4. Estimates are planning aids. Confirm quantities, coverage and prices with your supplier before purchasing. Found an error? Report it.
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