Choose each wall shape
Use rectangular wall, triangular gable, wall + gable, or direct known siding area.
Exterior materials
Siding Calculator
Estimate exterior siding area, siding squares, whole packages or pieces, extra material, and optional material cost. Combine multiple walls and gables, subtract actual surface-area exclusions, and use the packaging information for the siding product you plan to buy.
Quantity estimator only.This calculator does not choose siding type, thickness, exposure, overlap, fastening, substrate, weather barrier, flashing, wind or fire performance, accessory quantities, structural suitability, or code requirements.
How to use it
Estimate siding in four steps
Combine the project
Add repeated wall groups and subtract only the actual surface-area exclusions you choose to deduct.
Set your allowance
Choose the extra percentage that matches your product, cuts, layout, and project conditions.
Use manufacturer packaging
Enter coverage per package or pieces per siding square for the specific siding product.
Siding formulas
Rectangular wallArea = width × height
Triangular gableArea = ½ × base width × gable height
Wall + gableArea = width × wall height + ½ × width × gable height
Repeated sectionNet group = (gross area − excluded area) × quantity
AllowanceRequired area = base area × (1 + allowance ÷ 100)
Siding squaresSiding squares = required area ÷ 100 ft²
PackagesWhole packages = ceiling(required area ÷ package coverage)
PiecesWhole pieces = ceiling(siding squares × pieces per square)
Siding example
Four 40 ft × 10 ft rectangular wall sections have 1,600 ft² of gross area. If each section has 40 ft² of excluded area, the base area is 1,440 ft². With a 10% allowance, the project requires 1,584 ft², or 15.84 siding squares. If the selected product covers 200 ft² per package, the project needs 7.92 packages and therefore rounds to 8 whole packages.
Siding calculator FAQs
What is a siding square?
A siding square represents 100 ft² of siding coverage. This calculator keeps fractional siding squares instead of rounding them to whole squares.
Should I subtract every window and door?
The calculator does not make that estimating choice for you. Enter an actual excluded surface area only when you want it deducted, then choose your allowance separately.
How does wall + gable mode work?
It adds a rectangular wall and one triangular gable above it: width × wall height plus one-half × width × gable height.
Does the calculator assume package coverage?
No. Package coverage is product specific. Enter the manufacturer coverage for the siding you plan to buy.
Does the calculator assume pieces per square?
No. Different siding profiles can use different piece counts per square. Enter the manufacturer value for your exact product.
Why are packages or pieces rounded only once?
The calculator first combines the complete project requirement, then rounds the final purchase quantity upward. It does not independently round each wall group.
Can I use Metric measurements?
Yes. Wall lengths switch between feet and meters, area inputs switch between square feet and square meters, and package coverage converts with the measurement system.
Does this estimate accessories?
No. J-channel, starter strip, corners, trim, soffit, fascia, house wrap, flashing, fasteners, caulk, labor, tear-off, and disposal are outside this v1 quantity calculator.
Can I save or share an estimate?
Yes. After a successful calculation, the current project can be stored in the page URL when the URL remains within a conservative size limit.
Reference methodology
Geometry is calculated directly from entered dimensions. A siding square is treated as 100 ft². Manufacturer coverage or pieces-per-square values remain user-entered because installed coverage and packaging vary by siding product and profile. Unit conversion uses the international foot relationship of exactly 0.3048 meter.
Assumptions and limitations
- Rectangular-wall mode uses width × height.
- Triangular-gable mode uses one-half × base width × gable height.
- Wall + gable mode includes one rectangular wall and one triangular gable above it.
- Direct-area mode expects actual siding surface area.
- Excluded area is actual surface area per repeated section and must be smaller than that section's gross area.
- The allowance percentage is user supplied and applied after net section areas are combined.
- One siding square equals 100 ft²; siding squares remain fractional in the results.
- Package coverage and pieces per siding square are manufacturer-supplied inputs, not hidden defaults.
- Whole package or piece quantity is rounded only once after the complete project requirement is combined.
- Piece-equivalent purchased coverage is a mathematical conversion from pieces per square, not a cut-layout simulation.
- Material cost includes only the entered package or piece price and excludes taxes, delivery, accessories, labor, tear-off, and disposal.
- This calculator does not determine siding exposure, overlap, thickness, grade, fastening, substrate, weather-resistive barrier, flashing, structural adequacy, wind/fire performance, or code compliance.