Angle and percentage of gradient are two completely different concepts, yet you can readily convert one into the other. The reason this is true is that you can actually measure a slope in terms of angle instead of the more conventional method. Angles are denoted as fractions of a circle. One degree, for example, is a full circle divided by 360. Gradient is a ratio of vertical and horizontal movement. A one to one gradient, where horizontal and vertical movement is equal, is 100 percent gradient. The same gradient expressed as an angle is 45 degrees.
Things You'll Need
 Scientific calculator

Enter the degrees of angle into the calculator. For example, if the angle is 30 degrees, enter 30.

Press the "TAN" (Tangent) key on the calculator. For an angle of 30, the calculator should read 0.577350269.

Multiply by 100. In the preceding example, 30 degrees equals 57.73502692, which you can round up to 58 percent grade.
References
 "Student Calculator Math"; Ralph A. Oliva, et al; 1980
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