Slope and Grade Calculator

Take the arctangent of the grade divided by 100. For a 10% grade that is atan(0.10), which the tool reports as 5.710593137 degrees. The relationship is grade = tan(angle) times 100.

It means 1 unit of vertical rise for every N units of horizontal run, so N equals 100 divided by the percent grade. A 1:10 ratio is a 10% grade, a 1:1 ratio is a 45 degree slope, and a 1:50 ratio is a gentle 2% ramp.

No. Percent grade is rise over run times 100, while the angle is the arctangent of that same ratio. They stay close near zero (a 5% grade is about 2.86 degrees) but diverge sharply as the slope steepens, since a 100% grade is only 45 degrees.

It is the straight-line length measured along the slope, equal to the square root of rise squared plus run squared. It appears only in Rise and run mode, because percent grade and angle describe the steepness without fixing an actual length.

Percent grade divides rise by run, so a run of zero would divide by zero and describe a vertical wall rather than a slope. The tool rejects a run of zero or less and asks for a positive horizontal distance.

Any angle strictly between -90 and 90 degrees. At exactly 90 or -90 the slope is vertical and the grade is infinite, so those values are refused. Negative angles and negative grades describe a downhill slope.

No, only their ratio matters. Rise 10 and run 100 gives the same 10% grade whether the numbers are feet, meters, or inches, as long as both use the same unit. The slope distance comes back in that same unit.

Values are rounded to nine decimal places, which is far finer than any field survey or construction tolerance. A 10% grade returns exactly 5.710593137 degrees rather than a truncated 5.71.

Yes. Every conversion runs in your browser with plain trigonometry, nothing is uploaded, and there is no sign-in. You can use it offline once the page has loaded.