Quick Calculator
Calculate slope percent, find rise from slope and run, or find run from slope and rise.
What Is Percentage of Slope?
Slope percentage (also called grade) describes how steep a surface is by comparing the vertical change to the horizontal change. It is widely used in construction, civil engineering, landscaping, roads, drainage design, ramps, roofing, and hiking trail planning.
A slope of 10% means the elevation changes by 10 units vertically for every 100 units horizontally. The larger the percentage, the steeper the incline.
Slope Percentage Formula
The core formula is straightforward:
Slope (%) = (Rise / Run) × 100
- Rise = vertical change in height
- Run = horizontal distance covered
- Slope (%) = steepness expressed as a percent grade
Important: rise and run must use the same unit (feet with feet, meters with meters, etc.). If your units are mixed, convert first.
How to Use This Percentage of Slope Calculator
1) Find slope percent from rise and run
Select Find slope % from rise and run, enter both values, and click Calculate. The tool also returns the equivalent slope angle in degrees.
2) Find rise from slope percent and run
Select Find rise from slope % and run, enter a grade and horizontal distance, and the tool computes the vertical rise.
3) Find run from slope percent and rise
Select Find run from slope % and rise, enter the grade and vertical rise, and the calculator solves for required horizontal distance.
Percent vs Degrees vs Ratio
Slope can be represented in multiple ways. Here are common equivalents:
| Slope (%) | Rise:Run Ratio | Approx. Angle (degrees) |
|---|---|---|
| 5% | 1:20 | 2.86° |
| 8.33% | 1:12 | 4.76° |
| 10% | 1:10 | 5.71° |
| 25% | 1:4 | 14.04° |
| 50% | 1:2 | 26.57° |
| 100% | 1:1 | 45.00° |
Practical Applications
- Driveways: checking comfort and vehicle clearance.
- Ramps: confirming accessibility standards and safe use.
- Road design: evaluating climb and descent limits.
- Drainage: ensuring water moves away from structures.
- Landscaping: planning grading and retaining solutions.
- Roofing: converting roof pitch concepts into percent grade.
Worked Example
Suppose a path rises 1.8 m over a horizontal distance of 24 m.
Slope (%) = (1.8 / 24) × 100 = 7.5%
So the path grade is 7.5%. In degrees, this is approximately arctan(0.075) = 4.29°.
Common Mistakes to Avoid
- Using diagonal length instead of horizontal run.
- Mixing units (for example feet for rise and meters for run).
- Confusing 1:12 ratio with 12% grade (it is 8.33%).
- Forgetting that very steep values can become unsafe for access and drainage.
FAQ
Is a higher slope percentage steeper?
Yes. As slope percentage increases, the incline becomes steeper.
Can slope percentage be negative?
Yes. A negative value indicates a downward slope in the chosen direction of travel.
How do I convert slope percentage to angle?
Angle (degrees) = arctan(slope% / 100). This calculator handles that conversion automatically.
Can I use this for both metric and imperial units?
Absolutely. Just make sure rise and run are in the same unit system.