Calculating your sloped roof area is straightforward once you know the Roof Area 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 Roof Area Calculator.
What is Roof Area?
The Roof Area calculation tells you your sloped roof area from a few simple inputs. The figure you are solving for here is the sloped roof area.
The Roof Area formula
The core formula is:
Sloped roof area = Roof footprint length × Roof footprint width × √(Pitch run ^ 2 + Pitch rise ^ 2) ÷ Pitch runHere is what each input means:
- Roof footprint length — a value measured in m. Example: 10 m.
- Roof footprint width — a value measured in m. Example: 8 m.
- Pitch rise — a number. Example: 6.
- Pitch run — a number. Example: 12.
How to calculate it step by step
- Write down the roof footprint length (for example, 10 m).
- Write down the roof footprint width (for example, 8 m).
- Write down the pitch rise (for example, 6).
- Write down the pitch run (for example, 12).
- Apply the formula above to get your sloped roof area.
- Double-check the result with the Roof Area Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Roof footprint length | 10 m |
| Roof footprint width | 8 m |
| Pitch rise | 6 |
| Pitch run | 12 |
| Sloped roof area | 89.44 |
| Footprint area | 80.00 |
With roof footprint length of 10 m, roof footprint width of 8 m, pitch rise of 6 and pitch run of 12, the sloped roof area works out to 89.44.
Example 2
With roof footprint length of 20 m, roof footprint width of 8 m, pitch rise of 6 and pitch run of 12, the sloped roof area works out to 178.89.
| Result | Value |
|---|---|
| Sloped roof area | 178.89 |
| Footprint area | 160.00 |
Example 3
With roof footprint length of 5 m, roof footprint width of 8 m, pitch rise of 6 and pitch run of 12, the sloped roof area works out to 44.72.
| Result | Value |
|---|---|
| Sloped roof area | 44.72 |
| Footprint area | 40.00 |
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 Roof Area Calculator does it instantly, for free, with the formula and a worked example built in.
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