How to use the roof pitch and rafter calculator
Find the roof pitch angle, slope percentage and rafter length per metre of run from rise and run. Enter rise, run in the fields above; the pitch angle, slope as percentage, rafter length per metre of run are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “roof pitch angle”, “roof slope calculator”, “rafter length per run”, “calculate roof pitch and rafter”, “find pitch angle”.
Formula
Variables
- rise — Rise (cm)
- run — Run (cm)
Worked example
With rise = 4 cm, run = 12 cm, the calculator gives pitch angle ≈ 18.43495 °; slope as percentage ≈ 33.33333 %; rafter length per metre of run ≈ 1.054093 m.
Frequently asked questions
What is the roof pitch and rafter calculator used for?
Find the roof pitch angle, slope percentage and rafter length per metre of run from rise and run. It helps with questions such as “roof pitch angle”, “roof slope calculator”, “rafter length per run”.
What is the formula for the roof pitch and rafter calculation?
Pitch angle (°) = atan(rise / run). Slope as percentage (%) = rise / run × 100. Rafter length per metre of run (m) = √(rise × rise+run × run) / run. Here rise is rise (cm), run is run (cm).
What inputs do I need for the roof pitch and rafter calculator?
You need rise in cm, run in cm. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the roof pitch and rafter calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the roof pitch and rafter result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.