Ramp Calculator – ADA Accessibility & Slope Specifications
Calculate ramp length and ADA compliance for accessibility
Table of Contents
How to Use
- Enter the vertical rise (height to overcome)
- Enter the desired slope ratio (e.g., 1:12 for ADA)
- Select unit system (feet or meters)
- Click calculate to get ramp specifications
- Check ADA compliance status
What is ADA Compliance?
The Americans with Disabilities Act (ADA) establishes minimum accessibility standards for public and commercial facilities. For ramps, the ADA requires a maximum slope of 1:12, meaning one inch of vertical rise for every 12 inches of horizontal run.
This translates to a maximum grade of 8.33% or an angle of approximately 4.76 degrees, ensuring ramps are navigable by wheelchair users and others with mobility challenges.
ADA Ramp Requirements
- Maximum slope: 1:12 (8.33% grade)
- Minimum width: 36 inches clear
- Maximum rise: 30 inches between landings
- Landings required at top, bottom, and direction changes
- Landing size: minimum 60 inches deep
- Handrails required on both sides for rises over 6 inches
- Edge protection required (curbs or barriers)
- Surface must be stable, firm, and slip-resistant
How to Calculate Ramp Length
To calculate ramp length, use the Pythagorean theorem:
- Determine vertical rise (height to overcome)
- Calculate horizontal run: rise × slope ratio
- Calculate ramp length: √(rise² + run²)
- Calculate angle: arctan(rise / run)
For example, a 2-foot rise with a 1:12 slope requires a 24-foot horizontal run and approximately 24.08 feet of ramp length.
Common Slope Ratios
| Slope Ratio | Grade (%) | Angle (°) | Use Case |
|---|---|---|---|
| 1:12 | 8.33% | 4.76° | ADA compliant - public access |
| 1:15 | 6.67% | 3.81° | More comfortable for users |
| 1:20 | 5.00% | 2.86° | Ideal for power wheelchair users |
| 1:8 | 12.50% | 7.13° | Maximum for temporary ramps |
| 1:6 | 16.67% | 9.46° | Not ADA compliant |
Ramp Construction Tips
- Always consult local building codes before construction
- Use non-slip materials for the ramp surface
- Ensure proper drainage to prevent water accumulation
- Install adequate lighting for nighttime use
- Consider weather protection (roof or canopy) in harsh climates
- Use contrasting colors for visibility
- Regular maintenance is essential for safety
- Hire licensed contractors for permanent installations
Frequently Asked Questions
- What is the maximum slope allowed for an ADA-compliant ramp?
- The maximum ADA-compliant slope is 1:12, meaning one inch of rise for every 12 inches of horizontal run. This equals a grade of 8.33% or an angle of approximately 4.76 degrees.
- How long does a ramp need to be for a 30-inch rise?
- For a 30-inch rise with a 1:12 ADA-compliant slope, you need a minimum horizontal run of 30 feet (360 inches), resulting in a ramp length of approximately 30.37 feet.
- Do all ramps need handrails?
- ADA requires handrails on both sides when the ramp rise exceeds 6 inches or the horizontal run exceeds 72 inches. Handrails must be between 34-38 inches high and extend beyond the ramp at top and bottom.
- Can I build a steeper ramp for temporary use?
- Temporary ramps can have a maximum slope of 1:8 (12.5% grade) for short periods, but they should not exceed a 3-inch rise. For anything longer or higher, use the standard 1:12 ADA slope.
- How wide does an accessible ramp need to be?
- ADA requires a minimum clear width of 36 inches between handrails. For better usability, especially if two wheelchairs need to pass, consider 48-60 inches wide.
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