Calculating your panels/boxes needed is straightforward once you know the Siding formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Siding Calculator.
What is Siding?
The Siding calculation tells you your panels/boxes needed from a few simple inputs. The figure you are solving for here is the panels/boxes needed.
The Siding formula
This calculation combines several inputs through a multi-step method rather than a single one-line formula. Enter the values below and the calculator resolves each step in order. The inputs it needs are:
- Wall area — a value measured in m². Example: 80 m².
- Coverage per panel/box — a value measured in m². Example: 2 m².
- Wastage allowance — a percentage, such as an annual rate. Example: 1%.
How to calculate it step by step
- Write down the wall area (for example, 80 m²).
- Write down the coverage per panel/box (for example, 2 m²).
- Write down the wastage allowance (for example, 1%).
- Apply the formula above to get your panels/boxes needed.
- Double-check the result with the Siding Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Wall area | 80 m² |
| Coverage per panel/box | 2 m² |
| Wastage allowance | 1% |
| Panels/boxes needed | 44 |
With wall area of 80 m², coverage per panel/box of 2 m² and wastage allowance of 1%, the panels/boxes needed works out to 44.
Example 2
With wall area of 160 m², coverage per panel/box of 2 m² and wastage allowance of 1%, the panels/boxes needed works out to 88.
| Result | Value |
|---|---|
| Panels/boxes needed | 88 |
Example 3
With wall area of 40 m², coverage per panel/box of 2 m² and wastage allowance of 1%, the panels/boxes needed works out to 22.
| Result | Value |
|---|---|
| Panels/boxes needed | 22 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Siding Calculator does it instantly, for free, with the formula and a worked example built in.
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