Plumbing Slope Calculator
Calculate the minimum drain pipe slope and total drop needed based on pipe diameter and run length per IPC/UPC code.
Inputs
Results
Min Slope
0.25 in/ft
How to Use This Calculator
- Enter Pipe Diameter (inches) — common drain sizes are 1.5, 2, 3, and 4 inch.
- Input Pipe Run Length (ft) — the horizontal distance the drain must travel.
- Review Minimum Slope (in/ft) per code (typically 1/4 inch per foot for drains 3 inch and under).
- Check Total Drop Needed (inches) and Recommended Slope.
- Use Slope Degrees and Slope Percent when marking slope on a laser level.
What each input means
- Pipe Diameter
- Interior diameter of the drain pipe.
- Pipe Run Length
- Horizontal distance of the drain pipe run.
How this is calculated
Worked example, using the default values
- Identify Input ParametersPipe Diameter = 2, Pipe Run Length = 20 = 2 input(s) provided
- Calculate Min SlopeMin Slope0.25 = 0.25
- Calculate Total Drop NeededTotal Drop Needed5 = 5
- Calculate Recommended SlopeRecommended Slope0.25 = 0.25
Engine last updated . Checked against 3 independently-derived tests — how we verify calculators.
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