Slope can be expressed as percent, degrees, rise per metre or a 1:n ratio. The Slope calculator converts between these forms without treating them as equivalent numbers.
Slope (%) = rise ÷ horizontal distance × 100. A 10 cm drop over 5 m is 2%. This also means 2 cm of rise or fall per horizontal metre.
Percent is not degrees
A 5% slope corresponds to arctan(0.05), about 2.86°, not 5°. This distinction matters when drawings and product instructions use different conventions.
For 2% over 7.5 m, the rise is 7.5 × 0.02 = 0.15 m, or 15 cm. The corresponding angle is only about 1.15°.
Horizontal versus inclined distance
The percentage formula uses horizontal distance. A tape laid directly on a steep ramp measures the inclined length, which is a different value. Identify horizontal, vertical and inclined dimensions before calculating.
The 1:n form expresses the same geometry differently: 1:20 equals 5%. Inclined length can be obtained with Pythagoras from horizontal distance and rise.
The calculator converts geometry; it does not decide the required regulatory or technical slope for a roof, ramp, drain or terrace. Obtain the target value from the relevant project specification.
For an outdoor aggregate layer use the Gravel calculator; for a concrete element use the Concrete calculator.
