Road Grade Calculator
Enter a vertical rise and a horizontal run to get the grade as a percentage and the slope angle in degrees — the two ways every road sign, trail map, and ramp spec describes steepness.
Percentage and angle at once
Enter the rise and run and the calculator returns the grade as a percentage ((rise / run) × 100) and the slope angle in degrees (arctan of rise / run) together.
Use the horizontal run
The run is the horizontal distance, not the length of the sloped surface — use a negative rise for a downhill grade.
What is road grade?
How steepness is measured
The road grade is how steep a road, trail, ramp, or driveway is — how much it climbs or drops for a given horizontal distance. This road grade calculator takes two measurements, the vertical rise and the horizontal run, and turns them into the two numbers everyone uses to describe steepness: the grade as a percentage and the slope angle in degrees. It is the figure behind highway warning signs ("8% grade ahead"), accessibility ramp limits, railway gradients, and the climb categories on a cycling route.
Enter a vertical rise and a horizontal run to get the grade as a percentage and the slope angle in degrees instantly.
The grade is the rise divided by the run, expressed as a percentage, and the angle is the arctangent of that same ratio.
grade % = (rise / run) × 100The percentage and the angle describe the same slope two ways. The percentage is a ratio — 8% means 8 metres of rise for every 100 metres of horizontal run — while the angle is the geometric inclination from the horizontal. Use the same length unit for both the rise and the run; because the grade is a ratio, the unit cancels out and the result is unit-free.
Suppose a road rises 8 m over a horizontal run of 100 m.
Divide rise by run
8 / 100 = 0.08 — the rise-over-run ratio that defines the slope.
Multiply by 100 for the grade
0.08 × 100 = 8% — the grade as a percentage.
Take the arctangent for the angle
arctan(0.08) = 4.5739° — the same slope expressed as an angle from the horizontal.
The two outputs describe the same steepness in the two units you will meet in the real world. A grade percentage is the most common on roads and trails: a 5% grade is a gentle but noticeable climb, the steepest a wheelchair ramp may use is roughly 8% (about 4.6°), most mountain roads sit between 6% and 12%, and the world's steepest streets reach around 35% (about 19°). The angle in degrees is what surveyors, roofers, and engineers reach for. The key thing to notice is that the two are not the same number: a 100% grade is not "vertical" — it means the rise equals the run, which is a 45° angle. Grade percentages keep climbing past 100% for anything steeper than 45°, while the angle approaches a hard ceiling of 90°. A negative rise gives a negative grade and angle, describing a descent rather than a climb.
The formula is exact, but it depends on measuring the right distance.
Use the horizontal run, not the slope length
The run must be the horizontal distance covered, not the length of the sloped surface you would walk or drive along. On gentle grades the two are almost identical, but on steep slopes the slope length is noticeably longer than the horizontal run, and using it would understate the grade. If you only know the slope length and the rise, work out the horizontal run first with the Pythagorean theorem before entering it here.