Slope & Grade Calculator
Calculate slope percentage, grade, and angle for drainage and grading.
Slope & Grade Calculator
What This Calculator Does
The Slope and Grade Calculator computes the percent grade, angle in degrees, and ratio from a given rise (vertical change) and run (horizontal distance). Enter the rise and run in feet to instantly see the slope expressed three ways - percent, degrees, and ratio.
Slope and grade calculations are essential for drainage, grading, driveway design, and accessibility ramps. The ADA requires ramps to have a maximum slope of 8.33% (1:12 ratio). Building codes require 1-2% grading away from foundations for proper drainage. Driveways should have a maximum 10% slope for safe vehicle access. Each application uses a different expression of the same calculation.
The calculator provides all three common formats simultaneously so you can apply the result to any standard - whether you're reading a code requirement in degrees, a grading spec in percent, or an ADA guideline in ratio form.
How to Use
- Measure the vertical rise of your slope in feet (the total drop or elevation change).
- Measure the horizontal run in feet (the distance over which the rise occurs).
- Enter both values into the calculator fields above.
- Click "Calculate" to get the grade in percent, angle in degrees, and ratio.
- Compare your result against the relevant building code requirement.
Reference Table
| Grade % | Angle (deg) | Ratio | Application |
|---|---|---|---|
| 1% | 0.6deg | 1:100 | Minimum drainage |
| 2% | 1.1deg | 1:50 | Foundation drainage standard |
| 5% | 2.9deg | 1:20 | Patio/terrace slope |
| 8.3% | 4.8deg | 1:12 | ADA ramp max |
| 10% | 5.7deg | 1:10 | Driveway max slope |
| 15% | 8.5deg | 1:6.7 | Walkway max slope |
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