Fiber Cement Lap Siding Calculator
Enter the house size, the gable ends and every opening and get fiber cement lap boards by the exposure and the board length you enter, with trim pieces and corner posts. Hardie board is a trademark of its maker and is named here only because people search for it; this calculator is not from or endorsed by that maker.
A ready-made setup of the Siding Calculator.
Estimates for planning, not professional advice. Read the full notice.
Example: a house with fiber cement lap boards
164 fiber cement 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 | fiber cement boards | 164 |
| J-channel | J-channel pieces | 7 |
| Corner posts | corner posts | 4 |
| Starter strip | starter strip pieces | 12 |
Save on this device
Saved projects
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Worked example: a house with fiber cement lap boards
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 fiber cement 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"
Boards by exposure
Boards for the example house, and boards in one square, by exposure of a course
| Exposure | Boards in one square | Boards for the example house |
|---|---|---|
| 5 in | 20 | 229 |
| 6 in | 16.67 | 191 |
| 7 in | 14.29 | 164 |
| 8 in | 12.5 | 143 |
| 9 in | 11.11 | 127 |
Each row is worked out on its own for the example house and board length, with the waste allowance added once. The exposures are sizes entered for the table, not a maker's list.
Questions
How many pieces of fiber cement siding are in a square?
It depends on the exposure. A square is one hundred square feet; divide that by the area one board covers, its length times its exposure. The exposure table shows boards per square at a range of exposures for the board length in the example.
Is this a Hardie board siding calculator?
It counts lap boards of any maker from the length and exposure you enter. Hardie is a trademark of its owner, and nothing here is from or endorsed by that owner.