When constructing a wall, a ramp or a driveway, it is important to know the taper in both angle of rise or degrees from vertical. While the actual framing and construction will often use the taper in inches per foot, many plans and regulations state the allowable taper or slope in degrees. The two things can be equated with some simple formulas.
Convert any fractional inch measurement to a decimal inch equivalent. For instance, convert 1/4 inch to 0.25 inch. Use at least four decimal places for accuracy in your calculations.
Divide the decimal inch by 12 to arrive at the decimal foot taper per foot.
For example, 1.25/12 = 0.1042.
Convert the decimal foot taper to an angle in degrees by taking the arctangent of the taper. The arctangent is sometimes labelled atan or tan-1 on calculators. For example:
Atan(0.1042) = 5.94 degrees.
You can round this to -14.4 degrees Cor short distances.