About this calculator
Grade and fall for driveways, patios, paths and land drainage, in every format.
How it’s calculated
Grade % = rise ÷ run × 100. Degrees = atan(rise ÷ run).
Worked example
With these inputs:
- I know
- Rise and run
- Rise / drop
- 150 mm
- Run (horizontal)
- 3 m
the result is:
- Grade
- 5%
- Rise / drop
- 150 mm
- Ratio
- 1 : 20
- mm per metre
- 50 mm
- Slope length
- 3 m
Tips from the trade
- Patios: a fall of at least 1 in 50 (2%) away from buildings, the Concrete Manufacturers Association’s minimum for paving.
- Grass slopes steeper than about 1:3 (33%) are hard to mow.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and SANS 10400 (the National Building Regulations) and your local municipality before ordering.