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Home / Calculators / Slope Grade & Ratio Calculator

Slope Grade & Ratio Calculator

Turn rise and run into slope ratio, percentage grade, and angle — for algebra homework, ramps, roofs, roads, and drainage. Free, instant, works on your phone.

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Enter rise and run using the same unit — the unit itself doesn't affect the result, only the ratio between the two numbers.

Common slope thresholds for reference
Use caseTypical max/standard
ADA-compliant ramp (US)1:12 (8.33%)
Comfortable wheelchair ramp1:16–1:20 (5–6.25%)
Standard roof drainage (min)2% (about 1:50)
Typical residential roof pitch4:12 to 9:12 (33–75%)
Steep road grade warningAbove 8–10%
Standard stair pitch30°–35°

General reference only — always confirm exact requirements against your local building code, since standards vary by jurisdiction and application.