One slope, four notations — percent, degrees, inches per foot, and H:1V on one triangle
Every slope notation is rise ÷ run in a different dialect: 6″ over 10 ft is 5%, 2.86°, ⅝″ per foot, and 20H:1V — the same slope. Plumbing specs speak in/ft, ADA speaks percent, grading plans speak H:1V. And percent ≠ degrees: a 100% grade is 45°, not 90°.
What this diagram shows
A diagram showing that every slope notation is the same rise-over-run number. A shallow triangle represents ground falling 6 inches over a 10-foot horizontal run — the IRC R401.3 minimum grading away from a foundation. Four cards translate that one slope: 5 percent grade, from rise divided by run times 100; 2.86 degrees, from the arctangent of rise over run; five-eighths of an inch per foot, from 12 times rise divided by run; and a 20H:1V grading ratio, from run divided by rise. A caution notes that percent and degrees are different scales — a 100 percent grade is a 45-degree angle, not 90 degrees. Plumbing and flatwork specs are written in inches per foot, accessibility rules in percent, and grading and retaining-wall specs in H:1V ratios, but they all reduce to rise over run.
Slope Calculator
Free slope calculator: convert rise and run to percent grade, degrees, inches per foot, and H:1V ratio — plus total fall over your run. No signup.
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