Slope & Grade Calculator
Convert between rise/run ratio, percentage grade, and angle in degrees — for ramps, roofs, and roads.
🔒 Runs entirely in your browser — nothing here is ever uploaded
About the Slope & Grade Calculator
Converts between rise/run (as lengths), percentage grade, and angle from horizontal in degrees — enter any two of rise, run, or angle and it solves for the third, plus the ratio and grade percentage.
- Enter any two of Rise, Run, or Angle.
- Leave the third field blank.
- Read the solved value, along with the grade percentage and rise:run ratio.
Rise = 4, Run = 48 (a standard 1:12 ADA-style ramp): angle ≈ 4.76°, grade ≈ 8.33%, ratio 1 : 12.00.
| Ratio (Rise:Run) | Grade % | Angle |
|---|---|---|
| 1:12 (ADA max ramp) | 8.33% | 4.76° |
| 1:20 | 5% | 2.86° |
| 4:12 (common roof pitch) | 33.3% | 18.43° |
| 1:1 | 100% | 45° |
Grade percentage and angle only agree closely at shallow slopes, and diverge sharply as a slope steepens — a 100% grade is a 45° angle, not vertical. Confirm your local building code's specific ramp/roof/drainage slope minimums separately (e.g. ADA ramps commonly cap at a 1:12 ratio, about 8.33% grade).
- • A 1:12 ratio is the common maximum for ADA-compliant ramps.
- • Grade percentage can exceed 100% (anything steeper than 45°) — don't mistake a 100%+ grade for an error.
- • Run = 0 (a vertical rise) makes grade % and the ratio undefined, even though the angle is a well-defined 90°.
- U.S. Access Board — ADA Standards, ramp and running slope requirements — accessed 2026-08-31