Calculate the required fall (drop) of a pipe over a given length for a target slope percentage.
How to Use the Pipe Slope Calculator
Enter the "Pipe Length (m)" for the pipe run you are installing.
Enter the "Required Slope (%)" you want to achieve (defaults to 1%).
Click "Calculate" to see the required fall in meters and millimeters over the pipe run.
Frequently Asked Questions
Fall = Pipe Length × (Slope % ÷ 100). For example, a 20m pipe run at 1% slope needs 0.20m (200mm) of fall from one end to the other.
A common minimum is 1-2% (roughly 1/8 to 1/4 inch of fall per foot), though exact requirements depend on your local plumbing code and pipe diameter — see the Drainage Pipe Slope Calculator for diameter-based recommendations.
Too flat a slope can cause solids to settle and clog the pipe; too steep a slope can cause liquids to drain faster than solids, also leading to blockages. Staying within the recommended range avoids both issues.
Yes, it's completely free and requires no sign-up.