Siding Calculations
How Many Squares of Siding Do I Need?
Published June 9, 2026
A “square” is a construction-industry unit equal to 100 square feet of wall coverage. It’s used for both roofing and siding to simplify pricing and ordering, since it lets contractors and suppliers talk about quantity without referring to a specific product’s exact panel or board size.
Why squares instead of square feet?
Square feet describes an area. Squares describe a purchasing unit. A supplier can quote “$450 per square installed” and that price applies whether you’re using vinyl, fiber cement, or wood — the unit stays constant even though the underlying panel or board size varies dramatically between materials.
How to calculate your siding squares
- Add up your total wall area (length × height for each wall).
- Add your gable area (base × rise ÷ 2 for each gable).
- Subtract the area of windows, doors, and garage doors.
- Add your waste allowance (commonly 10–20%, depending on complexity).
- Divide the result by 100.
For example, a home with 1,580 sq ft of net siding area and a 10% waste allowance needs:
1,738 ÷ 100 = 17.38 squares
Most suppliers will round this up to the next whole or half square when quoting material.
Does house square footage equal siding squares?
No — this is one of the most common misconceptions homeowners run into. A home’s listed square footage measures floor area, not exterior wall area. Two homes with the same floor plan can need very different amounts of siding depending on wall height, roofline complexity, and how many openings they have.
Calculate it automatically
Use the Siding Squares Calculator for a quick net-area-to-squares conversion, or the full Siding Calculator to build up your area from individual wall, gable, and opening measurements.