Slope and gradient
Same rise and run, four ways of saying the slope. Useful for ramps, drainage falls and setting-out checks.
Method
Gradient = rise/run. Percent = gradient × 100. Angle = arctan(rise/run). 1 in N = run/rise.
Worked case: 0.15 m rise over 3 m run is 5%, 2.86°, and 1 in 20.
What to write beside the result
A review can only check this figure if the inputs sit next to it. Write the value, the unit and the assumption the form used. A diameter in millimetres and a diameter in metres are not the same reading. A force in kilonewtons divided as if it were newtons is a thousand-fold error.
The result is the arithmetic on this page. It is not a utilisation, not a selected product, and not a clause from a standard. If the number is going into a shared container, name the page, the date and the inputs. The file-name checker does not read the calculation.
Logic: how this figure is built.
How to read a slope
Slope can be a percentage, a ratio or an angle. A rise of 1 m in 10 m is 10%, 1 in 10, and about 5.7°. The page reports the conversions. It does not say the slope is allowed.
Rise and run must be the same unit. A 50 mm kerb upstand over 2 m is 2.5%, not 50%. Horizontal distance, not slope distance, is the run in this convention.
A drainage fall, a ramp and an embankment batter do not share a limit. Approved Document M, a highway standard and a drainage specification are different documents. This page is the geometry only.
Use it to check a level difference before it is written into a schedule. It does not set out the points.
- Related: horizontal curve
- setting-out logic
Last checked 3 October 2026. Worked figures are scenarios. See methodology and the disclaimer.