Slope Percent Calculator
Calculate signed percent slope, angle, straight slope distance and horizontal-to-vertical ratio from rise and horizontal run in metres or feet.
Convert a vertical rise and horizontal run into percent slope and an angle. The calculator preserves uphill and downhill signs and also gives the straight inclined distance between the two endpoints. Metres and international feet are available, provided both input distances use the selected common unit.
How to use this tool
- Enter the signed vertical change along the direction of travel.
- Enter a positive horizontal run, measured in plan rather than along the slope.
- Select the common distance unit.
- Read percent slope, angle and the horizontal-to-vertical magnitude ratio.
Formula
grade = rise / run; percent slope = 100 × grade; angle = atan(grade)
The straight slope distance is √(rise² + run²). The angle is measured from the horizontal in degrees and remains between −90° and +90° for positive run. Horizontal-to-vertical ratio uses magnitudes; the sign is carried by grade and angle.
Example
A rise of 1,000 ft over a horizontal run of 2,000 ft gives 1,000 / 2,000 × 100 = 50% slope. The angle is arctan(0.5), approximately 26.5651°. The horizontal-to-vertical ratio is 2 : 1.
Frequently asked questions
Does 100% slope mean vertical?
No. A 100% slope has equal rise and horizontal run, giving 45°. A vertical line has zero horizontal run and no finite percent slope; this calculator rejects that denominator.
Can percent slope exceed 100?
Yes. It means the vertical change is greater than the horizontal run. For example, 700 units of rise over 500 units of run gives 140%.
Can I use distance measured along a hillside?
Not as the run. The inclined distance is longer than the horizontal projection unless the ground is level. Using it directly understates the percent slope.
Does this describe an uneven route?
It describes the straight endpoint geometry. A route with changing grades has a longer path and varying local slopes. The result does not evaluate local drainage, construction tolerances or a regulatory slope limit.
Sources
Last updated: 2026-10-30