๐ Slope & Grade Calculator
Enter the horizontal run and vertical rise to calculate the slope as a percentage grade, an angle in degrees, a "1:x" ratio, and the actual slope distance. Useful for ramps, DIY stairs, or figuring out how steep a road grade is.
How to use
- Enter the horizontal run (in meters).
- Enter the vertical rise (in meters).
- The grade percentage, angle, ratio, and slope distance are calculated automatically.
How the calculation works
This tool expresses the slope of a road or ramp in several ways from its horizontal run and vertical rise. Grade (%) = rise รท run ร 100 Angle (degrees) = arctan(rise รท run) Ratio (1 : x) = 1 : (run รท rise) Slope length = โ(runยฒ + riseยฒ) Road signs give gradients as percentages: rising 8 m over 100 m is an 8% grade. As an angle that is only about 4.6ยฐ, so percentages and degrees are very different numbers; 45ยฐ equals 100%.
Worked example
Run 100 m, rise 8 m Grade: 8% Angle: about 4.57ยฐ Ratio: 1 : 12.5 Slope length: about 100.32 m Wheelchair ramps are commonly limited to 1:12 (about 8.3%); Japan's accessibility guidelines recommend 1/12 indoors and 1/15 outdoors.
Things to be aware of
- Maximum road gradients are set by road design standards according to road type and design speed.
- Roof pitch in Japan is often given in "sun" (rise per 10 horizontal): a 4-sun pitch is 40%, about 21.8ยฐ.
- Grades above 100% are steeper than 45ยฐ.
FAQ
What does slope as a percentage mean?
It's the rise expressed as a percentage of the run. For example, a road with 8m of rise over 100m of run has an 8% grade.
What does the "1:x" ratio mean?
It shows how many units of run correspond to 1 unit of rise. Accessibility ramp codes often specify a minimum like "1:12" using this notation.
What's the difference between angle (degrees) and grade (%)?
Grade is the rise-to-run ratio expressed as a percentage, while angle is the tilt from horizontal expressed in degrees. They scale differently โ a 45-degree angle corresponds to a 100% grade.