Siding Calculator
Siding squares and cost for house walls from area.
What it does
Siding sells by the square, one hundred square feet of wall, just like roofing. Wall area minus doors and windows plus a cuts allowance gives squares, and trim pieces cover the corners the field math leaves.
The tool above takes wall area with openings and waste in either system. It returns squares, material area, and cost at your price.
Gables complicate rectangles with triangles that waste more in cuts. Measure each gable as half of base times height and add it to the walls before subtracting openings.
Material profiles change coverage slightly. Wide panels cover faster with fewer seams while narrow profiles waste more around openings, which the waste share absorbs.
How to use
- Switch the unit system first: imperial for ft2, metric for m2.
- Measure all walls including gables.
- Subtract doors, windows, and big openings.
- Set waste by complexity and order full squares.
Formula
- 100 ft2
- One siding square of coverage.
- net
- Siding area after openings come out.
- waste
- Cuts around openings, gables, and corners.
Gable triangles add base times height divided by two each. Two gables on a 30 ft wide, 8 ft tall peak add 240 ft2 before waste.
Worked example
Example: 1500 ft2 walls, 200 openings, 10% waste, $250 per square
Walls 1500 ft2, openings 200, waste 10%.
- Net: 1500 - 200 = 1300 ft2.
- With waste: 1300 x 1.10 = 1430 ft2.
- Squares: 1430 / 100 = 14.30.
- Cost: 14.30 x $250 = $3,575.00 before trim.
Reference table
| Walls | Net | Squares |
|---|---|---|
| 1200 ft2 | 1100 | 12.10 |
| 1500 ft2 | 1300 | 14.30 |
| 2000 ft2 | 1800 | 19.80 |
| 2500 ft2 | 2300 | 25.30 |
Limits
- Field siding only. Trim and accessories excluded.
- Gable math needs separate triangles.
- Repairs tie into existing profiles and lots.
- Labor varies widely by height and access.
Common mistakes
- Measuring the footprint instead of wall area.
- Forgetting gable triangles entirely.
- Skipping the waste share on cut up walls.
- Ordering trim after the siding sells out.
- Ignoring old siding removal and disposal.
Try it yourself
Quick checks. Answers sit tucked under each question.
1000 ft2 walls, no openings, no waste. Squares?
1000 / 100 = 10 squares.
Metric: 140 m2, 18.6 openings, 10% waste?
Net 121.4. Then 121.4 x 1.10 = 133.54 m2.
Questions
What is a square of siding?
One hundred square feet of wall coverage.
How much waste should I add?
Ten percent for plain walls, fifteen with gables and many openings.
Do I subtract windows?
Yes, doors and windows come out before the waste multiplier.
How do gables count?
Each triangle adds half of base times height to the wall area.
What about trim pieces?
Corners, J channels, and starters count separately by linear feet.
Can new siding cover old?
Sometimes over sound flat siding. Rotted or wavy walls need strip first.