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.
Enter rise and run using the same unit — the unit itself doesn't affect the result, only the ratio between the two numbers.
—Ratio
—Percentage grade
—Angle
—Decimal slope (m)
Common slope thresholds for reference
Use case
Typical max/standard
ADA-compliant ramp (US)
1:12 (8.33%)
Comfortable wheelchair ramp
1:16–1:20 (5–6.25%)
Standard roof drainage (min)
2% (about 1:50)
Typical residential roof pitch
4:12 to 9:12 (33–75%)
Steep road grade warning
Above 8–10%
Standard stair pitch
30°–35°
General reference only — always confirm exact requirements against your local building code, since standards vary by jurisdiction and application.