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Road grades, ramps, and roof pitches are often described as a percentage slope. This tool calculates that percentage from the rise (vertical change) and run (horizontal distance), and also converts it to the equivalent angle in degrees.
How it works
Slope percentage is rise divided by run, times 100. The equivalent angle is the arctangent of rise/run, converted from radians to degrees.
- Enter rise (vertical change).
- Enter run (horizontal distance).
- Click Calculate to see your results.
Examples
A road grade sign
A road that rises 5 meters over a 100 meter horizontal run has a slope of 5/100 × 100 = 5%, which corresponds to an angle of about 2.86°.
Who should use it
- Calculating road, trail, or ramp grade percentage from survey measurements.
- Converting a roof pitch or ramp specification between percentage and angle.
Industry applications
- Civil engineering and road design
- Construction (ramps, roofing)
- Accessibility compliance (ADA ramp slope requirements)
Advantages
- Gives both the percentage grade and the equivalent angle in one calculation.
- Works for any rise and run, including very steep values.
Limitations
- Undefined when run is 0 (a purely vertical rise).
Common mistakes to avoid
- Assuming slope percentage and angle in degrees scale the same way — they don't; percentage grade grows much faster than angle for steep slopes.
Best practices
- For construction and road specifications, always double check whether a plan calls for percentage grade or angle in degrees, since they are not interchangeable without conversion.
Tips
- For accessibility ramps, remember most codes specify a maximum percentage grade (often 8.33% or less) rather than an angle — check the applicable code directly.