AlienCalc — Real tools, slightly extraterrestrial

Slope Calculator

Calculate the slope of a roof, terrain, or ramp in seconds. Enter the height (rise) and horizontal length (run) to get the slope as a percentage, in degrees, the hypotenuse, and the ratio.

Enter the height (elevation change) in meters
Enter the horizontal length in meters

Slope result

Slope in %

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Slope in degrees

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Hypotenuse (actual length)

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Ratio (rise/run)

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How to calculate a slope?

  • Roof pitch – Roof pitch is usually expressed as a percentage or in degrees. A tile roof requires at least a 30% slope (about 17°).
  • Terrain slope – For terrain, slope is calculated as rise divided by horizontal run. Useful for rainwater drainage or landscaping.
  • Access ramp – An accessible ramp should not exceed a 5% slope over a maximum length of 10 m, with rest landings.

Useful references

A 100% slope corresponds to a 45° angle (the rise equals the horizontal run). For roofing: flat tiles > 40%, interlocking tiles > 30%, slate > 40%, zinc or metal sheeting > 5%. For terraces, allow a 1 to 2% slope for water drainage.