Calculators/ Framing & Exterior/Siding Calculator
Siding Calculator
Squares of siding, trim and starter strip.
Siding Calculator
ft
ft
ft²
ft²
%
Siding is sold by the square, the same hundred-square-foot unit as roofing. Gable ends are the part people forget, and on a steep roof they can add a surprising amount of area.
How this is calculated
- Gross area = wall perimeter × height, plus the gable triangles (half the base × the height of each gable).
- Subtract doors and windows, then add 10% waste. Go to 15% if the elevation has many openings or corners.
- Divide by 100 for squares. Starter strip runs the full perimeter at the bottom course.
Frequently asked questions
How do I measure a gable end?
It is a triangle: half the width at the base times the vertical height from the eave line to the ridge.
How much siding waste should I allow?
Ten percent on a simple box, fifteen on a house with dormers, bays or many windows.