Siding Calculator
Estimate how many squares of vinyl, fibre cement or wood siding you need for a house.
About the Siding Calculator
Enter the wall perimeter and height, the gables, the area of windows and doors, and a waste allowance. The calculator gives the siding to order in squares, square feet and square metres.
Siding is sold by the square, 100 square feet. Measure the perimeter and wall height, add each triangular gable (½ × width × height), subtract windows and doors, then add 10% for cuts and overlaps (15% for complex walls or diagonal patterns). Trim, J-channel and corner posts are ordered separately by length.
The formula
Squares = (perimeter × height + Σ ½ × gable width × height − openings) × (1 + waste) ÷ 100
Worked example
160 ft of wall 9 ft high, two 30 × 8 ft gables, 220 ft² of openings, 10% waste
- Walls 1,440 + gables 240 − openings 220 = 1,460 ft²
- × 1.1 = 1,606 ft²
- 16.06 squares
Questions people ask
How much waste should I allow?
10% for simple walls, 15% with many openings or angles.
Do I subtract small windows?
Many installers subtract only large openings, which builds in extra.