Road Grade Calculator
Enter any two of grade (%), angle (°), rise, or run to instantly calculate the missing values and classify the slope.
Known Values
Enter any two fields and leave the third blank (or enter all three).
%
°
units
units
Results
Enter two values and click Calculate.
Grade
—
%
Angle
—
degrees
Rise
—
units
Horizontal Run
—
units
Slope Length (hypotenuse)
—
units
Slope Classification Reference
| Class | Grade | Angle |
|---|---|---|
| Flat | 0 – 2% | 0 – 1.15° |
| Gentle | 2 – 8% | 1.15 – 4.57° |
| Moderate | 8 – 15% | 4.57 – 8.53° |
| Steep | 15 – 30% | 8.53 – 16.70° |
| Extreme | > 30% | > 16.70° |
Summary
Enter any two of grade (%), angle (°), rise, or run to instantly calculate the missing values and classify the slope.
How it works
- Select which two values you know: grade %, angle, rise, or run.
- Enter the known values in their respective fields.
- Click Calculate to instantly compute the remaining values.
- Review the slope classification (flat, gentle, moderate, steep, or extreme).
- Use the results for road design, driveway planning, or ADA compliance checks.
Use cases
- Verify a driveway grade meets local building code limits (usually 10–15%).
- Convert road slope percentage to degrees for earthwork calculations.
- Estimate rise and run for a road segment given a target grade.
- Check ramp grades against ADA wheelchair accessibility requirements (max 8.33%).
- Calculate the elevation change over a known horizontal distance.
- Convert surveyor angle readings to grade percentages for design drawings.
- Evaluate hillside road feasibility before construction.
- Compare grades of multiple road segments in a grading plan.
Frequently Asked Questions
Last updated: 2026-07-23 ·
Reviewed by Nham Vu