Siding Calculator
Siding material and squares for the exterior walls of a building.
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Net area = perimeter × wall height + gable area − openings
Squares = net area ÷ 100
Lineal feet (lap) = net area ÷ board exposure
Run the calculation to see each step with your own numbers.
150 ft perimeter, 9 ft walls, 180 ft² of gables, 120 ft² of openings, 7" exposure bevel siding, 10% waste.
Net area = 1,350 + 180 − 120 = 1,410 ft²
Squares = 14.1 → order 15.5 with 10%
Lineal feet = 1,410 ÷ (7/12) = 2,417 ft → order ≈ 2,659 ft
- Gable area is entered by you (½ × gable width × gable rise for each). The Roof Pitch Calculator gives the gable rise from the width and pitch.
- Only openings larger than about 10 ft² are worth deducting — small windows are covered by waste.
- Lineal feet assumes the siding is ordered by the piece; panel/sheet siding is ordered by area — leave exposure at 0.
- House wrap, trim, corner boards, flashing, furring and fasteners are separate.
- What is siding 'exposure'?
- The height of each course that stays visible after the next course laps over it. 8-in bevel siding is typically installed at a 7-in exposure, so a 'square' of it is more lineal feet than the board's face width suggests.
- How do I get the gable area?
- For each gable, it's half the gable width times the gable rise. The Roof Pitch Calculator gives the rise from the width and the roof pitch. Add all the gable triangles together for the one input.
- Lap siding or panel siding?
- For lap siding, enter the board exposure and the calculator gives lineal feet to order by the piece. For panel or sheet siding, leave exposure at 0 and order by the square-foot area or squares.
Squares & coverage
A siding "square" = 100 ft² (1 roofing square = 100 ft² of roof surface. Universal roofing-trade convention (NRCA).). Lineal feet = area ÷ exposure — standard lap-siding coverage geometry.
About the Siding Calculator
The Siding Calculator turns a building's exterior wall dimensions into a net siding area, squares, and (for lap siding) lineal feet by exposure — the visible height of each course after the one above laps over it. Enter the wall perimeter and height, add the triangular gable areas, and deduct large openings. Only openings over about 10 ft² are worth subtracting. Trim, corner boards, house wrap and flashing are separate.
What you enter
- Wall perimeter — Total length around the building at the walls you're siding.
- Wall height (eave)
- Total gable / dormer area — Add the triangular gable areas: ½ × width × gable rise, each.
- Openings to deduct — Total area of windows and doors. Deduct only openings over ~10 ft².
- Board exposure (lap siding only) — Exposed face height per course — e.g. 7" for 8" bevel siding. Leave 0 for panel/sheet siding.
- Waste allowance — Default 10%. Adjust to your own allowance — the exact figure is always shown too.
What you get back
- Net siding area — the exact result of the calculation.
- Squares (100 ft²) — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
- Lineal feet (lap siding) — 0 for panel siding. = net area ÷ board exposure.
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
Related calculators
- Vinyl Siding Calculator — Vinyl siding panels, trim and accessories for a wall area.
- Wall Square Footage Calculator — Wall area for one or more walls, with openings deducted.
- Sealant Calculator — Tubes of sealant / caulk for a joint of a given length, width and depth.
- Roof Pitch Calculator — Roof angle, slope factor and rise-in-12 pitch from a rise and run.
Part of the Siding calculators.