Slope Percentage Calculator
Calculate slope percentage from rise and horizontal run, or convert an angle, grade, or 1-in-N ratio into every other common slope format.
Written and checked by TheToolNet Editorial Team · Last reviewed: September 20, 2026 · Editorial method
Calculate slope grade, angle, and ratio
How slope percentage is calculated
grade (%) = rise ÷ horizontal run × 100
A rise of 1 over a horizontal run of 12 is 8.333% and about 4.764°. Use horizontal run—not the sloping surface length. A negative rise represents a fall.
Which slope format should you use?
Road, mountain, and construction grades are often percentages. Drawings may use 1:N, while geometry uses degrees. The formats describe the same incline, but they are not interchangeable numbers.
Related slope tools
Check a wheelchair ramp geometry, calculate pipe fall, or convert a measured map distance with the topographic slope calculator.