Vinyl Siding Calculator

About this calculator

Vinyl siding is sold by the square — a roofing-and-siding trade unit equal to 100 square feet of coverage — with each square typically packaged as two boxes. This calculator takes your wall perimeter and height to find the gross wall area, subtracts the area of doors and windows, adds a waste allowance (commonly 10-15% to cover cuts, corners, and mismatched panels), and converts the result into squares and boxes plus the starter strip needed to anchor the first course.

Homeowners planning a re-siding project and contractors quoting materials use this to avoid two costly mistakes: under-ordering (which risks running out mid-job on a discontinued color or lot) and over-ordering (tying up cash in unused boxes). Getting the waste factor right matters more on complex facades with many corners, gables, and openings than on a simple rectangular wall.