DIY & materials
Roof pitch and slope Calculator
Calculate roof angle, slope length and rectangular pitched area. This free roof pitch and slope calculator shows the calculation and its assumptions so you can compare your own figures.
Your results
Calculate roof angle, slope length and rectangular pitched area.
Calculated outcomes
- Pitch Percent
- 50%
- Slope Length M
- 4.472 m
Assumptions and estimates
- Method: Slope length = √(run² + rise²). Angle = arctan(rise ÷ run). Area = slope length × roof length × number of slopes.
- Rectangular equal slopes only. Overhangs, hips, valleys, dormers and structural loads are excluded.
Useful next steps
- Use Compare options to test an alternative side by side.
- Copy, print or download a record of this calculation when you need one.
Reports open your email app addressed to s@s1.ie with the public page address only. Your inputs are never added.
How the roof pitch and slope calculation works
Slope length = √(run² + rise²). Angle = arctan(rise ÷ run). Area = slope length × roof length × number of slopes.
Rectangular equal slopes only. Overhangs, hips, valleys, dormers and structural loads are excluded.
Using this calculator
- Enter your own figures in the labelled inputs. Keep the currencies, units and time periods consistent.
- Choose any applicable rate profile, pattern or assumption shown for this tool. Open additional inputs when relevant.
- Review pitch degrees and roof area m2, then read the stated assumptions and eligibility conditions before using the result.
Worked example
This is a static example using illustrative inputs, not facts about you or today’s date. The displayed eligibility selections and assumptions apply only to this example.
See example inputs
- Horizontal run per slope (m)
- 4
- Vertical rise (m)
- 2
- Roof length (m)
- 10
- Equal roof slopes
- 2
- Pitch Degrees
- 26.57 °
- Roof Area M2
- 89.443 m²