Siding Calculator
Estimate siding area, 100-square units, whole pieces, packages, purchased coverage and cost. Enter the usable coverage printed for the actual vinyl, lap, panel or metal siding product.
Siding calculator formulas
Gross wall area = total wall width × wall height + gable area
Net siding area = gross wall area − openings
Order area = net siding area × (1 + allowance ÷ 100)
Pieces = ceil(order area ÷ usable coverage per piece)
Packages = ceil(pieces ÷ pieces per package)
A siding square is 100 square feet. Metric areas are converted to square feet only for this traditional reporting unit; purchasing calculations remain in the selected input system.
Worked examples
| Walls and deductions | Coverage / allowance | Calculated quantity |
|---|---|---|
| 140 ft perimeter × 9 ft + 100 ft² gables − 180 ft² | 20 ft²/piece, 10%, 10/package | 65 pieces, 7 packages |
| 2,000 ft² direct − 250 ft² | 25 ft²/piece, 12%, 12/package | 79 pieces, 7 packages |
| 200 ft perimeter × 10 ft − 300 ft² | 18 ft²/piece, 5%, 8/package | 100 pieces, 13 packages |
| 40 m perimeter × 2.7 m + 10 m² − 15 m² | 1.85 m²/piece, 10%, 10/package | 62 pieces, 7 packages |
| 250 m² direct − 30 m² | 2.4 m²/piece, 8%, 6/package | 99 pieces, 17 packages |
| 60 m perimeter × 3 m + 20 m² − 25 m² | 1.5 m²/piece, 15%, 12/package | 135 pieces, 12 packages |
How to estimate siding
- Add the widths of all wall sections with the same height, or enter a measured gross wall area directly.
- Add the combined area of gables and other triangular sections.
- Subtract only openings or surfaces that will not receive siding.
- Use the product’s installed usable coverage, accounting for exposure and overlap.
- Enter an appropriate cutting allowance, package quantity and current price.
- Review the purchased coverage because whole-package rounding can exceed the selected allowance.
Important limitations
- The calculator treats all entered walls as one area and does not create a cutting layout.
- Coverage per piece must be the installed usable coverage; nominal dimensions can overstate coverage.
- Allowances vary with wall geometry, color matching, product type and installer practices.
- Openings may require extra trim even when their area is subtracted.
- Material totals exclude corners, channels, starter strips, soffit, fascia, flashing, weather barriers, fasteners, tax and delivery.
- The optional labor rate is area-based and does not include removal, repairs, access, permits or disposal.
Related calculators
- Square Footage Calculator
- Paint Calculator
- Wallpaper Calculator
- Roofing Calculator
- Board and Batten Calculator
Frequently asked questions
How many square feet of siding do I need?
Calculate the wall and gable area, subtract excluded openings, then add an allowance. The calculator performs these steps and preserves both net and order areas.
What is one square of siding?
One siding square equals 100 square feet. It is a reporting unit, not necessarily one carton or package.
Can I calculate vinyl, lap, panel or metal siding?
Yes, when you enter the correct installed usable coverage and package quantity for that product. Accessory requirements remain separate.
Should I subtract windows and doors?
Enter the combined excluded area. Remember that openings can reduce field coverage while increasing trim and cutting needs.
Does the calculator include gables?
Yes. Add their combined area. For a triangular gable, calculate base × height ÷ 2.
Why is purchased coverage higher than order area?
The calculator rounds pieces and packages upward. Package rounding may create additional material beyond the selected allowance.