Drainage Slope
1/4 inch per foot rule and variants.
Example
You enter
- Rise 1
- Run (same units as rise) 4
- Units rise_run
You get
- Inches per foot 3
- Percent 25 %
- Degrees 14.0362
- Fraction 0.25
Checked against published worked examples from: IPC.
Details, formula, and sources
Formula or tableSlope expressed as fraction (1/4 inch per foot), degrees, and percent. Standard horizontal-drainage slopes per IPC 2027 Table 704.1 (identical in 2021).
Source and editionIPC 2027 (International Plumbing Code). Section 704, Table 704.1.
Free accessFree read-only access at codes.iccsafe.org.
What governsEstimate. AHJ and licensed plumber / gas fitter govern. Verify against the IPC / IFGC edition adopted in your jurisdiction.
API field namesrise, run, units, in_per_ft, percent, degrees, fraction
- Minimum slope rule 1/4 in per ft for ≤ 2-1/2 in; 1/8 in per ft for 3 to 6 in; 1/16 in per ft for 8 in and largerIPC 2027 Table 704.1 (identical in 2021)