Siding Calculator
Enter the length, width and wall height of the house, its gable ends with their pitch, and every door and window, and get lap boards or vinyl panels, J-channel, corner posts and starter strip, with waste added once and each product rounded up once. The working is shown for an example.
Estimates for planning, not professional advice. Read the full notice.
Example: a house with lap siding
164 lap siding boards
- Net wall area 1,039 ft²
- J-channel pieces 7 J-channel pieces
- Outside corner posts 4 corner posts
- Starter strip pieces 12 starter strip pieces
Estimate for planning, from what you entered and the product data shown. Check product labels and your supplier before you buy.
Your project
Enter a size to see your total.
Each product is rounded up once for the whole project, so the total can be less than the items bought alone added together. A line counted from a cut layout (sheets, boards or tiles laid out piece by piece) is counted for each item and added.
Shopping list
| Item | Size | Buy |
|---|---|---|
| Siding pieces | lap siding boards | 164 |
| J-channel | J-channel pieces | 7 |
| Corner posts | corner posts | 4 |
| Starter strip | starter strip pieces | 12 |
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Worked example: a house with lap siding
Show the working
- Gross wall: the distance round the house times the wall height 140 ft × 8 ft = 1,120 ft²
- Openings: every door and window at its own size 81 ft² = 81 ft²
- Net wall: gross wall less the openings 1,120 ft² − 81 ft² = 1,039 ft²
- Add the waste allowance, once, to the net wall 1,039 ft² + 10 % waste = 1,142.9 ft²
- Divide by the area one piece covers: its length times the exposure 1,142.9 ft² ÷ 7 ft² = 163.27 pieces
- Round up once, to whole pieces 163.27 pieces = 164 lap siding boards
Assumptions
The figures behind the example. Sourced figures link to their source below; a default is a starting value to check against your label or supplier.
| Assumption | Value | Details and changes |
|---|---|---|
| Siding waste allowance | 10% | |
| Default A common allowance, not a sourced figure. Check your label or supplier. | ||
Feet and inches, like 12' 6"
Gable area by roof pitch
Area of one gable end of the example house, and its sloped edge, by roof pitch
| Roof pitch | Area of one gable | Net wall with two gables |
|---|---|---|
| 3/12 | 56.25 ft² | 1,232.5 ft² |
| 4/12 | 75 ft² | 1,270 ft² |
| 5/12 | 93.75 ft² | 1,307.5 ft² |
| 6/12 | 112.5 ft² | 1,345 ft² |
| 7/12 | 131.25 ft² | 1,382.5 ft² |
| 8/12 | 150 ft² | 1,420 ft² |
| 9/12 | 168.75 ft² | 1,457.5 ft² |
| 10/12 | 187.5 ft² | 1,495 ft² |
| 12/12 | 225 ft² | 1,570 ft² |
Each row is worked out on its own from the example house. The gable is the triangle under the roof across the house width; the pitch is read as rise in twelve.
Questions
How many squares of siding does a house need?
Take the net wall area, add the waste allowance once, and divide by the area one piece covers. The squares figure is only the same area written in hundreds of square feet, so the calculator never rounds it before dividing; it rounds the piece count up once at the end.
How do I deduct windows and doors?
Enter each opening at its own size. The calculator takes the area of every door, window and large door off the gross wall once, and it asks again if an opening is taller than the wall or wider than the longest wall.
Does vinyl need a different count from lap boards?
Only the area one piece covers changes. A vinyl panel often shows two courses, so its coverage is its length times the courses times the exposure. Choose the profile and the courses, and check the piece length and exposure on your own label or with your supplier.