Elevation Calculator
Turning Rise and Run Into a Slope Angle
Terrain steepness gets described two overlapping ways — as an angle in degrees or as a grade percentage — and the two aren't linearly related to each other, which is a common source of confusion. A 45° slope is a 100% grade, not a 45% grade. This calculator takes a horizontal distance and vertical rise and returns both figures directly from the same right-triangle relationship.
The Formula
Grade % = (Rise ÷ Run) × 100
Rise and run must be in the same units — the ratio between them is unitless, so feet, meters, or any consistent unit works identically.
Reference Grades
| Rise : Run | Slope Angle | Grade % |
|---|---|---|
| 1 : 12 (ADA max ramp slope) | 4.76° | 8.33% |
| 5 : 100 | 2.86° | 5.00% |
| 1 : 1 | 45.00° | 100.00% |
The Americans with Disabilities Act sets a maximum running slope of 1:12 (8.33%) for accessible ramps — a widely referenced construction benchmark.
Where This Calculation Matters
- Trail and road grading — hiking trail difficulty ratings and road signage both commonly reference grade percentage, derived from exactly this rise/run relationship.
- Accessibility compliance — ramps, walkways, and parking lot slopes are checked against maximum allowable grades in building codes.
- Solar panel and structural design — converting a specified roof or panel angle into the rise-per-run figure used on construction drawings, or vice versa.
How to Use This Calculator
- Enter the horizontal distance (run) in your chosen unit.
- Enter the vertical rise in the same unit.
- Select Calculate to get the slope angle in degrees and the grade as a percentage.
Related Calculations
Mapping a route across real coordinates instead of a single slope? See the Distance Between Coordinates Calculator or scale a site plan with the Map Scale Calculator.