Siding Calculator

By Uzair Arshad , Senior Civil and Structural Engineer

Last updated: April 20, 2026

Use this siding calculator to estimate how much siding you need for your house or garage. Enter wall dimensions, gable areas, and window openings to get net square feet, squares, and a 2026 cost range by material type.

How to use this calculator

This free siding calculator estimates the total siding square footage you need for your home's exterior walls. Enter your house siding measurements below and the siding estimate calculator returns sq ft, squares, and cost estimates for vinyl siding, fiber cement, and engineered wood siding. Use it as a vinyl siding calculator for material takeoffs or for any siding type.

Enter your total exterior wall area in square feet. Measure each wall's width and height, multiply them, and add all walls together. For a home with four 8-foot-high walls (two at 40 feet and two at 25 feet), the total wall area is (40 x 8 x 2) + (25 x 8 x 2) = 1,040 sq ft.
Enter the gable width and height if your home has gable ends. Set both to 0 if you have no gables. If you have multiple gables, add the total gable area to your wall area in step 1 and leave these fields at 0.
Enter the total area of all windows and doors. A standard window is about 15 sq ft (3 x 5 feet). A standard entry door is about 21 sq ft (3 x 7 feet). Count your openings and multiply by these averages, or measure each one individually for more accuracy.
Set the waste factor. Use 10% for simple rectangular walls with few cuts. Use 15% for homes with many corners, bump-outs, or dormers. Use 20% for complex designs with multiple angles.
Click "Calculate siding" to see your results. The siding sq ft calculator shows total square feet, squares, and installed cost estimates for three popular siding materials.

Pro tip: Measure each wall separately instead of estimating from your home's floor area. Floor square footage does not equal wall square footage because it ignores wall height and the number of stories. A 1,500 sq ft single-story ranch and a 1,500 sq ft two-story colonial have very different siding needs.

How to measure a house for siding

Start at one corner and work clockwise. Use a tape measure or laser distance tool for each wall's width and height. Record every wall section separately, including bump-outs and garage walls. Multiply width by height for each section and add them up. This gives you the gross wall area for this siding calculator.

For gables, measure the base width and the height from the eave line to the peak. Plug these into the calculator's gable fields. If you have more than one gable, add them together and enter the combined area in the wall area field instead.

Assumptions and limitations

This siding calculator assumes flat exterior walls with standard framing. Results may vary for curved walls, log homes, or heavily textured surfaces. The gable calculation uses the triangle formula (half of base times height), which assumes a standard symmetrical gable. Irregular roof shapes need manual measurement.

Cost estimates reflect 2026 national averages for materials plus labor. Your actual cost depends on your region, contractor rates, wall prep work, and whether you remove old siding first. Always get 2 to 3 local quotes before committing.

Siding cost by material type (2026 installed prices)

Use this reference table to compare siding materials. Costs include materials and professional installation but not tear-off of existing siding.

Material	Cost/sq ft	Lifespan	Maintenance
Vinyl	$3 to $7	20-40 years	Low (wash annually)
Fiber Cement (Hardie)	$5 to $10	30-50 years	Repaint every 10-15 years
Engineered Wood (LP)	$4 to $8	25-30 years	Repaint every 10-15 years
Cedar	$6 to $12	20-40 years	Stain every 3-5 years
Metal/Aluminum	$4 to $9	40-60 years	Low (wash annually)

How the calculation works

Surface Area:
Gable Area = 0.5 × Gable Width × Gable Height
Gross Area = Wall Area + Gable Area
Net Area = Gross Area − Openings

Ordering:
Total with Waste = Net Area × (1 + Waste % / 100)
Siding Squares = Total with Waste / 100

Wall Area: Total exterior wall area in square feet
Gable Width: Width of gable end at the base in feet
Gable Height: Height from gable base to peak in feet
Openings: Total area of windows and doors in square feet
Waste %: Percentage added for waste and cut-offs (typically 10%)

This siding calculator uses a straightforward area formula with deductions for openings and an adjustable waste factor. Here's how to calculate siding square footage step by step, so you can verify every number the calculator produces.

Step-by-step breakdown

Start by adding up all rectangular wall sections. Then add any gable ends using the triangle area formula (half of base times height) because gable ends are triangular. Subtract windows and doors from the gross total, then apply the waste percentage. Finally, divide by 100 to convert square feet into siding squares. If you have multiple gables, measure each one and add the total gable area to your wall area input.

How to figure square footage for siding: a real example

Say you have a 1,600 sq ft ranch with 130 linear feet of perimeter and 9-foot walls. The gross wall area is 130 x 9 = 1,170 sq ft. You have two gables at 24 feet wide and 5 feet tall: 2 x (0.5 x 24 x 5) = 120 sq ft. The gross total is 1,290 sq ft.

Subtract 10 windows (150 sq ft), 2 doors (42 sq ft), and 1 garage door (112 sq ft) for 304 sq ft of openings. Net area: 1,290 - 304 = 986 sq ft. Add 10% waste: 986 x 1.10 = 1,085 sq ft or 10.9 squares. That tells you how much siding you need for this house.

Understanding siding squares

One square of siding covers 100 square feet. How many square feet in a siding square? Exactly 100. This is the unit that suppliers and contractors use to quote material. Vinyl siding panels are sold in bundles that cover 2 squares (200 sq ft) each. Hardie siding (fiber cement lap siding) comes in 12-foot planks at 5.25 to 12 inches wide, and you calculate the number of planks based on your total square footage divided by each plank's coverage area.

Why add waste?

Every siding project produces waste from cutting panels to fit around corners, windows, and at the ends of walls. A 10% waste factor is standard for simple rectangular homes. Bump-outs, bay windows, dormers, and complex rooflines increase waste to 15% or 20%. I learned this the hard way on a garage re-side where I ordered exactly the calculated amount and came up 3 panels short on the last wall.

Deducting windows and doors

Standard window sizes and their approximate areas for calculating square feet for siding:

Opening Type	Typical Size	Area
Single window	3 ft x 5 ft	15 sq ft
Double window	6 ft x 5 ft	30 sq ft
Picture window	6 ft x 4 ft	24 sq ft
Entry door	3 ft x 7 ft	21 sq ft
Sliding glass door	6 ft x 7 ft	42 sq ft
Garage door (single)	9 ft x 7 ft	63 sq ft
Garage door (double)	16 ft x 7 ft	112 sq ft

Add up all your openings and enter the total in the siding calculator. A typical home has 8 to 12 windows (120-180 sq ft), 2 exterior doors (42 sq ft), and 1 garage door (63-112 sq ft). That totals 225 to 334 sq ft of openings for an average home.

For a detailed cost breakdown by material type with real project examples, see our siding cost per square foot guide.

Common siding calculator mistakes to avoid

Forgetting gable ends is the most common error when calculating the amount of siding needed. A single large gable can add 60 to 120 sq ft of siding area. That is 1 to 2 extra squares of material you would have to reorder at a second delivery charge of $75 to $200.

Using floor area instead of wall area is another frequent mistake. A 1,500 sq ft single-story ranch has about 1,200 sq ft of wall area (assuming 130 linear feet of perimeter x 9 ft wall height = 1,170 sq ft). A 1,500 sq ft two-story has about 800 sq ft of wall area per floor because the perimeter is smaller, but you have two stories, so the total is similar. Always measure walls directly.

Frequently Asked Questions

How do you calculate square footage for siding?

Measure the height and width of each exterior wall and multiply to get the area. Add all walls together, then subtract windows and doors. Add 10% for cutting waste. A typical 2,000 sq ft home has about 1,200 to 1,600 sq ft of siding area after deducting openings.

How much siding do I need for a 1,500 square foot house?

A 1,500 sq ft home typically needs 1,000 to 1,400 sq ft of siding depending on wall height and window count. With standard 8-foot walls and average window coverage of 15%, plan for about 1,100 sq ft plus 10% waste. That comes to roughly 1,210 sq ft or 12.1 squares.

What is a square of siding?

A square of siding equals 100 square feet of coverage. Contractors and suppliers use squares as the standard ordering unit. A typical single-story ranch needs 10 to 15 squares. A two-story colonial needs 18 to 25 squares. Order an extra square to cover waste and future repairs.

How much does siding cost per square foot installed?

Vinyl siding costs $3 to $7 per sq ft installed in 2026. Fiber cement (James Hardie) runs $5 to $10 per sq ft. Engineered wood (LP SmartSide) costs $4 to $8 per sq ft. Cedar siding runs $6 to $12 per sq ft. Prices vary by region and contractor.

How do you calculate siding for a gable?

Measure the gable width at the base and the height from the base to the roof peak. Multiply width times height and divide by 2 (triangle formula). A gable 30 feet wide and 6 feet tall equals 30 x 6 / 2 = 90 sq ft. Add this to your total wall area before subtracting openings.

Do I need to remove old siding before installing new siding?

Vinyl siding can go over existing wood or vinyl in most cases without removal. Fiber cement and engineered wood need a flat surface, so stripping the old layer is recommended. Always check for rot, mold, or insect damage underneath. Most contractors charge $1 to $3 per sq ft for removal and disposal.