Elevation Grade Calculator
Turn a rise and run into grade percentage, angle in degrees, slope length, and ratio.
📐 What is the Elevation Grade Calculator?
The elevation grade calculator turns a rise and a run into the slope of a surface, expressed four ways: as a percentage grade, an angle in degrees, the actual slope length, and a rise-to-run ratio. It is the tool for anyone who needs to know how steep something is, from a wheelchair ramp to a driveway, a roof, a trail, or a graded building site.
Slope shows up across construction and civil work. Accessibility ramps must not exceed a set grade, drainage relies on land falling at the right slope, roads and driveways have comfort and safety limits, and roofs are specified by pitch. In each case you start with two measurements, the vertical rise and the horizontal run, and need to express their relationship in the units your code or plan uses, which might be a percentage, an angle, or a ratio.
A common mistake is confusing grade with angle. A 100 percent grade is not vertical; it is a 45 degree angle, because at 100 percent the rise equals the run. The two are linked by the arctangent function, so a modest 5 percent grade is only about 2.86 degrees. Another point of confusion is the slope length: the distance you actually travel up a slope is longer than the horizontal run, and equals the hypotenuse of the rise-run triangle.
This tool is useful because it converts one pair of measurements into every form of slope you might be asked for, and shows the geometry behind them. You enter the rise and run, pick a unit, and instantly see the grade, angle, slope length, and ratio, with the working laid out so you can check it against a spec.
📐 Formula
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 - Gentle land grade, 3 ft over 100 ft
Example 2 - Steep driveway, 10 ft over 50 ft
Example 3 - Road grade, 5 ft over 100 ft
❓ Frequently Asked Questions
🔗 Related Calculators
How do you calculate the grade of a slope?
Divide the rise (vertical change) by the run (horizontal distance) and multiply by 100 for the percentage grade. A 3 foot rise over a 100 foot run is 3 / 100 x 100 = 3 percent grade. Keep both measurements in the same unit.
What is the difference between grade and angle?
Grade is the rise divided by the run expressed as a percentage, while the angle is measured in degrees. They are related by the arctangent: angle = arctan(rise / run). A 100 percent grade equals a 45 degree angle, and a 5 percent grade is about 2.86 degrees.
How do I convert percent grade to degrees?
Take the arctangent of the grade written as a decimal. For a 10 percent grade, angle = arctan(0.10) = about 5.71 degrees. This calculator shows the angle in degrees automatically alongside the percentage grade.
What is the maximum slope for a wheelchair ramp?
The ADA sets a maximum of 1:12 for accessible ramps, which is one unit of rise for every 12 units of run, or about an 8.33 percent grade (roughly 4.76 degrees). Steeper ramps are harder and less safe to use, so 1:12 or gentler is the standard.
How do I calculate slope length from rise and run?
The slope length is the hypotenuse of the right triangle formed by the rise and run: slope = square root of (rise squared plus run squared). For a 10 foot rise and 50 foot run, slope = square root of (100 + 2500) = about 50.99 feet.
What is a 1:12 slope in percent?
A 1:12 ratio means 1 unit of rise for every 12 of run, which is 1 / 12 x 100 = about 8.33 percent. Ratios like 1:12, 1:20, and 1:8 are common in accessibility and drainage specifications; divide the run number into 100 to convert to a percentage.
What grade is too steep for a driveway?
Most guidance keeps driveways under about 15 percent, and ideally under 10 percent, to avoid scraping vehicles and to stay safe in ice or rain. Short sections can be steeper, but long steep driveways cause problems, so check local codes for limits.
Does the unit of measurement affect the grade?
No. Because grade is rise divided by run, the units cancel as long as both use the same one. A 3 metre rise over 100 metres and a 3 foot rise over 100 feet both give a 3 percent grade. The unit only matters for the slope length, which comes out in whatever unit you enter.