Measurement & Project Planning calculator
Slope Calculator
Calculate slope percentage, ratio and angle from vertical rise and horizontal run.
Calculate slope percentage, ratio and angle from vertical rise and horizontal run. Keep the dimensions and units consistent, then check the figures that describe the product or layout you will really use. In this calculation, rise versus horizontal run can change the answer materially. Use horizontal run rather than distance along the slope. A percentage grade and an angle are different representations of the same rise-to-run relationship.
What you need to enter
The Slope Calculator uses the following project information to calculate the result.
- Rise
- Run
Calculator result
Slope percentage, ratio and angle
How the Slope Calculator works
For slope expressed as percentage, ratio and angle, the calculator uses rise ÷ run expressed in multiple formats. The mathematics is only one part of the estimate: getting rise versus horizontal run right usually matters more to the real-world result than extra decimal places. Unit conversion happens before the calculation.
Slope Calculator worked example
Slope Calculator example: A 0.5 m rise over a 10 m horizontal run is a 5% grade and an angle of about 2.86°. The slope expresses the same geometry in the formats commonly used for setting out. Use the numerical result as the starting point, then verify rise versus horizontal run against the material, layout or equipment actually being used.
Important calculation assumptions
For slope expressed as percentage, ratio and angle, use horizontal run rather than distance along the slope. A percentage grade and an angle are different representations of the same rise-to-run relationship.
Frequently asked questions
What is the difference between slope percentage and slope angle?
Slope percent is rise divided by horizontal run multiplied by 100; angle is the arctangent of the same rise/run ratio. They describe the same geometry in different formats.
Should the run be measured along the slope?
No. Use horizontal run. Measuring along the sloping surface changes the ratio and gives the wrong percentage grade.
Can I use the Slope Calculator for drainage design?
It can express the geometry, but required drainage falls depend on the system, pipe size and applicable guidance. Use the calculated slope only as one design input.