Gradient to Percentage Calculator

Road signs show grades in percent, ADA ramps are specified as a ratio, and roofs often in degrees. Enter rise and run (any unit, both the same) or an angle and get all three forms.

Results update as you type.

Grade (percent slope): 7.5%
Angle: 4.289°
Ratio: 1 : 13.33

Steps

3 ÷ 40 × 100 = 7.5%
atan(3 ÷ 40) = 4.289°

Worked example

Example: a driveway rises 3 ft over 40 ft

3 ÷ 40 = 0.075
× 100 = 7.5% grade
atan(0.075) = 4.29°, ratio 1 : 13.3

The driveway has a 7.5% gradient (about 4.3°).

Formula

Grade % = Rise ÷ Run × 100

Angle = atan(Rise ÷ Run)

Ratio = 1 : (Run ÷ Rise)

A 100% grade is 45°, not vertical. ADA wheelchair ramps max out at 1:12, which is 8.33%.

Frequently asked questions

How do I convert a slope ratio to a percentage?

Divide 100 by the ratio's second number. 1:20 = 100 ÷ 20 = 5%.

What does a 6% grade mean on a road sign?

The road rises or falls 6 feet for every 100 feet of horizontal distance.

Is percent slope the same as degrees?

No. 10% is about 5.71°. Use the calculator to convert either way.

Last reviewed October 17, 2026 · Calculations run in your browser; nothing you enter is sent to a server.