Drain Pipe Fall and Ending Level Calculator
Calculate total pipe fall and ending invert level from run length, starting level and selected slope percentage.
Formula
Planning estimate. Check product specifications and local requirements before purchasing.
Worked example: Drain Pipe Slope Calculator
Measurements in this example
| Pipe run | 20 m |
|---|---|
| Required slope | 1 % |
| Starting invert level | 100 m |
Calculated quantities
| Total fall | 0.2 m |
|---|---|
| Ending invert level | 99.8 m |
What to check
This calculation uses: Pipe run, Required slope, Starting invert level. It returns: Total fall, Ending invert level.
Measure the run along the pipe route and use invert levels at the inside bottom of the pipe, not cover or ground levels.
Total fall equals pipe length multiplied by slope percentage divided by one hundred. The fall is subtracted from the starting invert.
Check the result against the drainage design and local requirements. A steeper line is not automatically better for every pipe or flow.
Do not reverse the levels. Follow the intended direction of flow and confirm that the outlet remains physically available.
Use the units beside each field. The values in the worked example are starting inputs; replace them with your measurements and the specifications of your material.
Compare alternatives
Open a tool, enter your measured dimensions, then save an estimate. Keep another version if you want to compare products or allowances.