Siding calculator
Add up the walls and gable triangles, take off the windows and doors, then add waste. A house with 140 ft of wall 9 ft high, two 30 ft gables 7.5 ft tall, ten 3 × 5 ft windows and two 3 × 7 ft doors has 1,293 sq ft of siding area; with 10% waste that is 14.22 squares, or 8 cartons at 2 squares per carton.
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How the calculator works
This follows the method in siding maker Kaycan's estimator: wall area plus gable area, minus windows and doors, gives the net surface; add 10% for waste; divide by 100 to get squares. A gable is a triangle, so its area is base × height ÷ 2. Cartons are rounded up to whole cartons and panels to whole panels.
Panel coverage by profile
One panel covers its length times its exposure, the part left visible once the next course overlaps it. Owens Corning's specification for its Fundamental Series Select vinyl siding gives these lengths and exposures and packs both profiles at 2 squares per carton (Owens Corning, via Sweets). The coverage and panels-per-carton columns are our arithmetic from those figures.
| Profile | Length | Exposure | Per panel | Panels per 2 squares |
|---|---|---|---|---|
| Double 4" (and Double 4" Dutch lap) | 12' 6" | 8" | 8.33 sq ft | 24 |
| Double 5" (and Double 5" Dutch lap) | 12' | 10" | 10.00 sq ft | 20 |
Other brands and profiles (vertical board and batten, shakes, fiber cement, engineered wood) have different sizes and carton counts. Enter the coverage printed on the carton or the maker's spec sheet.
Gable height from roof pitch
If you know the roof pitch, the gable height is half the gable width times the rise per 12 in of run, divided by 12. For a 30 ft gable:
| Pitch | Gable height, 30 ft base | Gable area |
|---|---|---|
| 4/12 | 5.00 ft | 75.0 sq ft |
| 5/12 | 6.25 ft | 93.8 sq ft |
| 6/12 | 7.50 ft | 112.5 sq ft |
| 8/12 | 10.00 ft | 150.0 sq ft |
| 10/12 | 12.50 ft | 187.5 sq ft |
| 12/12 | 15.00 ft | 225.0 sq ft |
Find your pitch with the roof pitch calculator.
Measuring tips
- Measure each wall along the bottom where the siding will start, and the height from there to the soffit. Walls of different heights are easiest entered one run at a time and added to the project list.
- Leave out areas you won't side, such as a brick skirt or a covered porch wall.
- Openings are subtracted at their outside trim size. Small openings like vents can be ignored; the waste allowance covers them.
- Trim, J-channel, starter strip, corner posts and soffit are bought by the piece and the linear foot, not by the square. Measure eaves, corners and opening perimeters for those.