Elevation Grade Calculator

Calculate percent grade, angle, and slope ratio from an elevation change and horizontal distance.

⏱ Updated: 18 Sep 2026

Calculator

Free elevation grade calculator: convert elevation change and horizontal distance into percent grade, angle, and ratio.

This is a planning estimate, not a survey. For drainage, grading, or accessibility compliance work, confirm actual site grades with a licensed surveyor.
Percent Grade
%
Angle
°
Ratio
1 :

A positive elevation change means the far end sits higher; a negative value means it slopes downward. Percent grade is the figure most drainage and road specs quote directly.

Enter an elevation change and horizontal distance to calculate percent grade, angle, and slope ratio. This is a planning estimate, not a survey.

How to Use the Elevation Grade Calculator

Enter the elevation change between two points and the horizontal distance separating them. A positive elevation change means the far point sits higher; a negative one means the ground drops away.

Grade shows up everywhere on a residential site plan: a driveway that shouldn't exceed 10–12% for safe winter traction, a drainage swale that needs a minimum 1–2% fall to actually move water, an accessible ramp capped by code at a much shallower slope than either. All of them are the same ratio expressed as percent grade, degrees, or a ratio, depending on which trade is reading the number.

The Formula

percent grade = (elevation change ÷ horizontal distance) × 100
angle = arctan(elevation change ÷ horizontal distance)
ratio = 1 : (horizontal distance ÷ elevation change)

The ratio form reads as "1 unit of rise for every X units of run" — a 1:20 ratio and a 5% grade describe the identical slope, just phrased for different audiences.

Treat this as a planning estimate. Actual site grading, drainage design, and accessibility-ramp compliance depend on precise survey data and often on soil and drainage conditions this calculator has no way to see — confirm real grades with a licensed surveyor before finalizing design work.