Geometry & drainage
Gradient from rise / fall and run
- where
- gradient denominator (1 in N)
- horizontal run (m)
- vertical fall (m; any unit you pick is converted)
- slope (fraction; the calculator shows %)
Explain this equation
Works out the gradient of an existing or planned pipe run from its fall and horizontal length. Use it to check a run against the gradient you need.
L is the horizontal run. h is the vertical fall. N is the gradient as 1 in N. s is the slope as a fraction, shown as a percentage.
Gradient is fall over run. Writing it as 1 in N means taking the run divided by the fall instead.
Sense check: 75 mm of fall over 6 m is 1 in 80, or 1.25%. A larger N means a flatter pipe.
Watch out: this gives geometry only, not drainage compliance.
Enter your values to see the result.
Good to know
Geometric result, not drainage compliance approval.
Sources
Results are arithmetic only. Worked examples are not recommended design settings. This library does not provide automatic gas pipe selection, live gas tightness tests, purging procedures, combustion acceptance limits, installation approval or commissioning certification. Manufacturer data and the applicable current method remain essential.