Roof pitch calculator
Estimate outputs: Roof angle, Slope, Slope factor. Adjust Roof rise, Roof run to match your project.
Estimate outputs: Roof angle, Slope, Slope factor. Adjust Roof rise, Roof run to match your project.
Inputs and units
Use the units shown beside each field. Replace the sample values with your measurements and the figures on the selected product packaging.
| Parameter | Example input |
|---|---|
| Roof rise | 40 cm |
| Roof run | 100 cm |
Formula and assumptions
Roof angleatan(Roof rise / Roof run) × 180 / π
SlopeRoof rise / Roof run × 100
Slope factorsqrt(1 + (Roof rise / Roof run)²)
ceil = round up; floor = round down; max = the greater value. Trigonometric angles are converted from degrees to radians.
Allowance is applied before rounding to whole packages. Whole units are rounded up; displayed decimals are rounded only for readability.
Roof calculations assume a simple rectangular surface or equal pitch slopes. Include overhangs in the entered plan dimensions; check overlaps and effective coverage.
Worked example
Sample values are examples, not product specifications. Run the calculation again with your own measurements.
| Result | Calculation |
|---|---|
| Roof angle | 21.8014° |
| Slope | 40% |
| Slope factor | 1.077 |
Related calculators
Related tools use separate measurements. Check their inputs before transferring quantities.
These are quantity estimates. Confirm product coverage, site conditions and required dimensions before ordering.