Calculate slope as a percentage grade, angle and ratio from rise and run.
Calculated instantly in your browser.
How do you calculate slope and grade from rise and run?
Grade = rise ÷ run × 100, angle = arctan(rise ÷ run), and slope length = √(rise² + run²). Use the same units for rise and run. For example, a rise of 1 over a run of 12 is an 8.33% grade, about 4.76°, or a 1:12 ratio — the common maximum for wheelchair ramps.
Understanding your result
Use the same units for rise and run. A 1:12 ratio (8.33%) is the common maximum for wheelchair ramps.
Formula and method
Grade = rise ÷ run × 100. Angle = arctan(rise ÷ run). Slope length = √(rise² + run²).
Assumptions and limitations
It converts a straight rise and run into a percentage grade, an angle, a ratio and the slope length. It describes a single constant gradient and assumes the rise and run share the same units; it does not model curved or varying inclines or check any specific building regulation for you.
Worked example
A rise of 1 over a run of 12 is an 8.33% grade, about 4.76°, or a 1:12 ratio.
How to use this tool
- Enter the rise (vertical change).
- Enter the run (horizontal distance).
- Press Calculate.
About the Slope & Grade Calculator
The Slope & Grade Calculator turns a rise and run into a percentage grade, an angle in degrees and a ratio, plus the slope length.
Who should use this tool
Builders and roofers setting pitches, accessibility planners checking ramp gradients, road and drainage designers, and hikers or cyclists gauging steepness who have a rise and a run and want the grade, angle, ratio and slope length worked out.
Benefits
- Gives grade, angle, ratio and slope length together
- Converts a rise and run into every common slope measure
- Useful for ramps, roofs, roads and drainage
- Loads fast and keeps working offline once opened
Practical use cases
- Checking a wheelchair ramp meets a gentle gradient
- Setting the pitch of a roof or driveway
- Working out drainage fall across a run of pipe
- Gauging how steep a trail or road really is
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Frequently asked questions
What is a 1:12 slope?
It means 1 unit of rise for every 12 of run — an 8.33% grade, the usual accessibility limit for ramps.
How do I convert a slope grade into an angle?
Take the arctangent of the rise divided by the run to get the angle in degrees. A rise of 1 over a run of 12 gives an 8.33% grade, which is about 4.76 degrees. Grade and angle describe the same steepness in two different ways.
What does a 1:12 slope mean?
A 1:12 ratio means the surface rises one unit for every twelve units travelled horizontally, which works out to an 8.33% grade. It is a common maximum gradient used for wheelchair ramps, giving a gentle, manageable incline over a longer run.