Case 1
- Rise
- 8m
- Run
- 100m
8.00%
Open with these valuesRoad Grade Calculator
8.00%
Result: 8.00 %Grade is the rise divided by the run, times 100: a road climbing 8 m over 100 m of map distance has a grade of 8 %. Percentage and degrees are the same slope told two ways — 8 % is 4.57°, and 100 % is not vertical but 45°, where rise and run are equal.
Worked examples
Case 2
- Rise
- 12m
- Run
- 100m
12.00%
Open with these valuesCase 3
- Rise
- -8m
- Run
- 100m
-8.00%
Open with these valuesHow it's calculated
grade % = (rise ÷ run) × 100
- StepMeasure the vertical rise, and enter it as a negative number for a descent.
- StepMeasure the horizontal run — the map distance, not the length of the road surface.
- ResultDivide rise by run and multiply by 100; both lengths must use the same unit.
Reference table
| Rise, run | Same slope as an angle | Grade |
|---|---|---|
| 0, 100 | 0°, level | 0 |
| 5, 100 | 2.86° | 5 |
| 8, 100 | 4.57° | 8 |
| 12, 100 | 6.84° | 12 |
| 41, 100 | 22.29°, San Francisco's steepest block | 41 |
| 50, 100 | 26.57° | 50 |
| 100, 100 | 45°, where rise equals run | 100 |
| -8, 100 | -4.57°, a descent | -8 |
Questions
How do I calculate road grade?
Divide the vertical rise by the horizontal run and multiply by 100: grade % = (rise ÷ run) × 100. A road that rises 8 m over 100 m of horizontal run has a grade of 8 %. The same slope as an angle is arctan(8 ÷ 100) = 4.57°.
What is the difference between grade percentage and degrees?
They describe the same slope two ways. The percentage is the rise-over-run ratio times 100, so 8 % means 8 m of rise per 100 m of run; the angle is arctan of that same ratio. A 100 % grade is 45°, not vertical, because at 45° the rise equals the run.
What counts as a steep road grade?
There is no single threshold, but the scale helps: 5 % is a gentle climb, 12 % already reads as steep. Ten blocks of public street in San Francisco exceed 30 %, and the steepest of them reaches 41 %. Even those stay below 100 %, which is 45° and not vertical at all.
What are rise and run?
The rise is the change in height and the run is the horizontal distance covered — not the length of the sloped surface itself. Use the same length unit for both; because the grade is a ratio, the unit cancels and the result is unit-free.
Can the grade be negative?
Yes. A negative rise means the road drops instead of climbing, which gives a negative grade and a negative angle. A rise of -8 m over a 100 m run is a grade of -8 % and an angle of -4.57°.
Sources and last check
Information, not professional advice.