calcs.homes
calcs.homes
Enter your home's perimeter and wall height to get exterior siding coverage and estimated cost, minus your windows and doors.
Estimate only — includes 10% waste for cuts and overlap.
We multiply house perimeter by wall height for gross wall area, subtract your entered window and door area to get net area, then add 10% for waste from cuts and overlap. In US units we divide that figure by 100, since siding is sold in "squares" of 100 sq ft each; metric results stay in square meters, matching how metric siding is typically priced.
Perimeter times height is a shortcut for total wall area that works because it treats the whole building's exterior as one continuous surface rather than measuring each wall separately, then subtracts total opening area in one step. The 10% waste allowance is the standard contractor buffer for angled cuts, corners, and pattern matching at seams — check whether your supplier's quoted coverage already builds in a waste factor before adding this one on top of it.
A square is a roofing and siding industry unit equal to 100 square feet of coverage — it's how most US suppliers price and package siding.
For a precise estimate, add up the area of all windows and doors and enter the total. For a rough estimate, many contractors just add 10-15% waste and skip the subtraction — either approach works with this calculator.