Siding calculator
Add up the length of the walls you’re siding, enter the wall height and the gable ends, and subtract windows and doors.
Siding needed
14.85 squares
- Square feet with waste
- 1,485 sq ft
- Wall area
- 1,350 sq ft before waste
How it works
Rectangular wall area is total wall length × height. Each gable end is a triangle, width × height ÷ 2. The calculator subtracts window and door openings, adds waste, and divides by 100, because siding is sold by the square (100 square feet).
Example
With total wall length 140 ft, wall height 9 ft, gable ends 2, gable width 30 ft, gable height (wall top to peak) 8 ft, windows and doors 150 sq ft, waste 10%, the answer is 14.85 squares.
Tips before you buy
- A standard door is about 21 sq ft and an average window about 15 sq ft. Add them up for the openings figure.
- Order trim, J-channel, corners and starter strip separately. They’re measured in linear feet.
- Use 10% waste for simple houses and 15% for lots of corners, dormers and gables.
Common questions
What is a square of siding?
100 square feet of wall coverage.
How much siding for a 40×30 house?
With 9 ft walls, two 30 ft gables 8 ft tall and 150 sq ft of openings, about 14.85 squares including 10% waste.
Should I subtract windows when measuring for siding?
Yes for large openings. Some installers skip small windows to build in extra material.