Slope Grade
5.00%
Angle
2.86°
Ratio
20.0:1
Grade
Gentle
5.00%
2.86°
20.0:1
100.12 ft
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Inputs
Result
Slope % = (5/100) × 100 = 5%. Angle = atan(5/100) × (180/π) = 2.86°. Ratio = 100/5 = 20:1. Length = √(25 + 10000) = 100.12 ft.
Inputs
Result
Slope % = (1/12) × 100 = 8.33%. This is the ADA maximum for wheelchair ramps (1:12 ratio). Angle = atan(1/12) × (180/π) = 4.76°.
Slope percentage = (Rise / Run) × 100. For example, a 5 ft rise over 100 ft run = (5/100) × 100 = 5% slope. This is the most common way to express grade in construction.
A 2% slope equals approximately 1/4 inch per foot (0.24 inches per foot exactly). This is the minimum recommended slope for lawn drainage and flat roof water runoff.
| Slope % | Inches per Foot | Ratio | Common Use |
|---|---|---|---|
| 1% | 0.12 in/ft | 100:1 | Minimal drainage |
| 2% | 0.24 in/ft | 50:1 | Lawn, flat roofs |
| 5% | 0.60 in/ft | 20:1 | Yard grading |
| 8.33% | 1.00 in/ft | 12:1 | ADA ramp maximum |
| 15% | 1.80 in/ft | 6.7:1 | Max driveway slope |
Most building codes limit residential driveways to 15% slope (about 8.5 degrees). Steeper driveways cause traction problems in wet or icy conditions and make it difficult to stop safely.
| Application | Max Slope | Angle | Notes |
|---|---|---|---|
| Parking lot | 5% | 2.9° | ADA accessible areas max 2% |
| Residential driveway | 15% | 8.5° | Check local codes |
| Garage entry ramp | 20% | 11.3° | Short runs only |
| Road (highway) | 6% | 3.4° | DOT standard |
The ADA requires wheelchair ramps to have a maximum slope of 8.33% (1:12 ratio), meaning 1 inch of rise for every 12 inches of run. Ramp runs cannot exceed 30 feet without a landing.
Slope % = tan(angle) × 100. For example, a 5° angle: tan(5°) = 0.0875, so 0.0875 × 100 = 8.75% slope. Conversely, angle = atan(slope% / 100) × (180/π).
| Angle (degrees) | Slope % | Ratio | Real-World Example |
|---|---|---|---|
| 1° | 1.75% | 57:1 | Nearly flat ground |
| 5° | 8.75% | 11.4:1 | ADA ramp (close to max) |
| 10° | 17.6% | 5.7:1 | Steep driveway |
| 30° | 57.7% | 1.7:1 | Steep hillside |
| 45° | 100% | 1:1 | Rise equals run |
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Last Updated: Jul 24, 2026
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