Percent Slope Calculator

Percent slope measures how steep a surface is by comparing the vertical rise to the horizontal run. It tells you how much elevation changes over a given distance—essential for roads, ramps, drainage, and trail design.

What is Percent Slope?

Percent slope is the ratio of vertical rise to horizontal run, multiplied by 100. A 10% slope means you gain 10 feet of elevation for every 100 feet of horizontal distance. The higher the percentage, the steeper the incline.

Formulas Used

Rise and Run Method

Percent Slope = (Rise ÷ Run) × 100

Divide vertical height by horizontal distance, then multiply by 100.

Angle Method

Percent Slope = tan(Angle) × 100

Use tangent of the angle in degrees to find slope percentage.

Reverse Calculation

Run = Rise ÷ (Percent Slope ÷ 100)

Find horizontal distance when you know the rise and slope.

Percent Slope Reference Table

This table shows slope values with corresponding angles and grade classifications:

Rise	Run	Slope (%)	Angle (°)	Ratio	Grade
1 ft	100 ft	1%	0.57°	1:100	Gentle
1 ft	50 ft	2%	1.15°	1:50	Gentle
1 ft	20 ft	5%	2.86°	1:20	Gentle
1 ft	16.67 ft	6%	3.43°	1:16.7	Gentle
1 ft	12.5 ft	8%	4.57°	1:12.5	Gentle
1 ft	10 ft	10%	5.71°	1:10	Moderate
1 ft	8 ft	12.5%	7.13°	1:8	Moderate
1 ft	6.67 ft	15%	8.53°	1:6.7	Moderate
1 ft	5 ft	20%	11.31°	1:5	Moderate
1 ft	4 ft	25%	14.04°	1:4	Steep
1 ft	3.33 ft	30%	16.70°	1:3.3	Steep
1 ft	2.86 ft	35%	19.29°	1:2.9	Steep
1 ft	2.5 ft	40%	21.80°	1:2.5	Steep
1 ft	2 ft	50%	26.57°	1:2	Steep
1 ft	1.5 ft	66.7%	33.69°	1:1.5	Steep
1 ft	1 ft	100%	45°	1:1	Steep
1.5 ft	1 ft	150%	56.31°	1.5:1	Steep
2 ft	1 ft	200%	63.43°	2:1	Steep
3 ft	1 ft	300%	71.57°	3:1	Steep
5 ft	1 ft	500%	78.69°	5:1	Steep
10 ft	1 ft	1000%	84.29°	10:1	Steep

Percent Slope Calculator