Siding Material Calculator

A siding material calculator returns the number of siding squares a house exterior needs. It multiplies the perimeter by wall height, subtracts door and window areas, adds waste, and divides by coverage per square, 100 sq ft by default, rounding up. A square is 100 sq ft of wall coverage.

Last reviewed September 2026Method & sources Report an error

Not to scale.

Siding Squares to Order

Includes a 10% waste allowance.

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Siding13 squares (100 sq ft)

Breakdown
Siding Squares to Order	13
Net Wall Area (openings subtracted)	1,098 sq ft
Adjusted Area (with waste)	1,207.8 sq ft
Building Perimeter	140 ft

How to Calculate Siding Material

Wall area for a rectangular building is its perimeter (`2 × (length + width)`) times wall height. Door and window area is estimated by count: 21 sq ft per standard door and 15 sq ft per standard window, the same practical assumption the Paint calculator uses. That area is subtracted, since siding doesn't go over an opening. A waste allowance is added for cuts around corners, openings, and pattern loss. The adjusted area is then divided by the coverage per square (100 sq ft by default, one "square," the same unit convention roofing uses) and rounded up to a whole square. Siding is typically ordered and priced by the square regardless of the specific product.

Example: 40 ft × 30 ft house, 9 ft walls, 2 doors, 8 windows, 10% waste

A 40 ft × 30 ft house, 9 ft walls, 2 doors, 8 windows, 10% waste, 100 sq ft/square: 1. Perimeter: 2 × (40 + 30) = 140 ft 2. Gross wall area: 140 × 9 = 1,260 sq ft 3. Openings: (2 × 21) + (8 × 15) = 42 + 120 = 162 sq ft 4. Net wall area: 1,260 − 162 = 1,098 sq ft 5. Adjusted for waste: 1,098 × 1.10 = 1,207.8 sq ft 6. Squares to order: 1,207.8 ÷ 100 = 12.08, rounded up to 13 squares

Siding Material: Compare Scenarios

Scenario	Siding Squares to Order	Net Wall Area (openings subtracted)	Adjusted Area (with waste)	Building Perimeter
Small (24×20 ft cottage)	7	630 sq ft	693 sq ft	88 ft
Medium (40×30 ft house)	13	1,098 sq ft	1,207.8 sq ft	140 ft
Large (60×40 ft two-story house)	38	3,438 sq ft	3,781.8 sq ft	200 ft

What Is Siding Material?

A siding material calculator converts a house's exterior wall dimensions into the number of siding "squares" needed to cover it. This is a general, product-agnostic estimate that works for any siding type sold by the square (vinyl, fiber cement, engineered wood, and more). For an exact panel or course count specific to vinyl siding's interlocking panel system, see the Vinyl Siding calculator instead.

Siding Material: Pros and Cons

Pros

Works for any siding product sold by the square, not tied to one specific material or panel system
Subtracts door and window area automatically rather than leaving that adjustment to the user
Uses the same "square" unit convention as the Roofing Material calculator, so the two are easy to reason about together for a full exterior remodel

Cons

Doesn't account for gable ends, dormers, or other non-rectangular wall sections. Add their area separately before running this calculator.
Doesn't include trim, corner posts, or J-channel. See the Vinyl Siding calculator for a full accessory takeoff specific to that product.
Assumes a simple rectangular footprint. An L-shaped or otherwise irregular house needs its perimeter and wall area calculated per wing and summed

Siding Material: What a Pro Checks

Add a gable end's area separately. Multiply its base by its height and divide by 2, then add that to the rectangular wall area this calculator covers below the eave line.
Plan closer to 15-20% waste instead of the 10% default on a house with a lot of corners, dormers, or architectural detail. More cuts mean more scrap.
Calculate an L-shaped or irregular footprint one wing at a time. Work out each section's perimeter and wall area separately, then add them together.

Frequently Asked Questions

How many squares of siding do I need?

Find your net wall area (perimeter × height, minus doors and windows), add a waste allowance (commonly 10%), then divide by 100 sq ft per square and round up. A 40 ft × 30 ft house with 9 ft walls needs about 13 squares.

What does a "square" of siding mean?

A square is a unit equal to 100 sq ft of wall coverage, the same convention roofing uses for shingles. It's a standard way contractors and suppliers price and order siding regardless of the specific product or panel size.

Does this work for vinyl siding specifically?

It gives a general square-footage-based estimate that applies to any siding type. For an exact panel count, starter strip, J-channel, and corner post takeoff specific to vinyl siding's interlocking panel system, use the Vinyl Siding calculator instead.

How much waste should I plan for siding?

10% is a reasonable default for a simple rectangular house. A home with a lot of corners, dormers, or architectural detail generates more cuts and scrap, so plan closer to 15-20% for a more complex exterior.

Do gable ends count toward the wall area?

This calculator estimates the rectangular wall area below the eave line only. A gable end's triangular area above that line needs to be estimated separately (base × height ÷ 2) and added to the total if it's also being sided.

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