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: 1:60 to 1:80 fall away from the house.
- 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 the Building Regulations before ordering.