Siding Material Calculator

Find the number of squares of siding material needed by entering the dimensions of the building below for a wall or gable. Optionally, include the number of doors and windows to refine the estimate.

Graphic showing how to measure the length and height of a rectangular wall for siding
Graphic showing how to get the dimensions for a gable by measuring the width of the gable and the height of the peak


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How to Measure for Siding

home with newly installed siding

If you’re planning a siding replacement project or preparing to install a new exterior, then the first thing you should do is estimate the size of the project. This step will help with estimating material and labor costs.

Siding is often estimated and priced by the square.

How Much is a Square of Siding

Square is a term used by contractors, installers, and building suppliers and is a unit of measure equal to 100 square feet of material.

Vinyl siding is commonly estimated by the square to determine how much labor and material is needed.

One square of siding will cover 100 square feet, and an average box of vinyl siding contains 2 squares of material.

Graphic showing that 1 square of siding is equal to 100 square feet

To find the number of squares of siding needed for an installation, measure the width and height of each wall in feet. Multiply the width and height to get the area of the wall in square feet.

Divide the square footage by 100 to get the number of squares needed for the wall.

For example, a wall that is 40ft wide and 12ft high will require 4.8 squares of material.

40 × 12 = 480
480 ÷ 100 = 4.8

How to Measure Gable Walls

Finding the square footage of a gable wall is similar to finding the square footage of a standard wall. Measure the width of the gable and the height of the gable, from the base of the triangle to the peak.

Then multiply the width and height, just like you would to find the area of a rectangle. Finally, divide the area in half to get the final square footage. Divide by 100 to get the number of squares.

For example, a 20ft wide gable that is 10ft tall will require 1 square of material.

20 × 10 = 200
200 ÷ 2 = 100
100 ÷ 100 = 1

It is a good idea to order additional material to account for angle cutoffs along the edge of the gable roof.

How to Account for Doors and Windows

A wall with doors and windows may require fewer squares of material to cover than a wall with no doors. To account for this overage in material, find the square footage of space that will not be covered in siding for the doors and windows and subtract that from the total square footage of the wall.

For example, an average door is 3ft wide by 7ft high. Subtract 21ft2 from the total square footage to account for a door. Windows vary in size, and the square footage can be found by multiplying the length and the width.

It is a good idea to account for waste during installation and order additional material. It is commonly recommended to order an additional 10% material to account for cutoffs, trim, and other waste.

Before you start your project

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Additional Siding Measurement and Installation Resources

For clapboard and lap siding, use our clapboard siding calculator to find the number of boards needed to cover the home. The board and batten siding calculator can estimate the material needed for a board and batten project.

Find the cost of siding installation in your area or find qualified installers.

Learn how to estimate siding materials needed for a siding installation project and learn how to find how many squares are needed.