How to Calculate Ramp Slope Ratio

Ramp Slope Ratio Formula:

\[ Ratio = \frac{Run}{Rise} \] \[ Ratio = 12:1 \text{ for 1" rise per ft run} \] \[ \text{Percentage} = \frac{Rise}{Run} \times 100 \]

Slope Ratio:

Slope Percentage:

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1. What is Ramp Slope Ratio?

The ramp slope ratio represents the relationship between the horizontal distance (run) and vertical height (rise) of a ramp. It's commonly expressed as a ratio (e.g., 12:1) or as a percentage, and is crucial for accessibility compliance and safety in construction.

2. How Does the Calculator Work?

The calculator uses the following formulas:

\[ Ratio = \frac{Run}{Rise} \] \[ \text{Percentage} = \frac{Rise}{Run} \times 100 \]

Where:

\( Run \) — Horizontal distance in feet
\( Rise \) — Vertical height in inches
\( Ratio \) — Run to rise ratio (unitless)
\( Percentage \) — Slope percentage (%)

Explanation: A 12:1 ratio means for every 12 feet of horizontal run, there is 1 inch of vertical rise. This corresponds to approximately 8.33% slope.

3. Importance of Slope Ratio Calculation

Details: Proper slope calculation ensures ramps meet accessibility standards (ADA requirements), provides safe and comfortable use for wheelchair users, and complies with building codes for maximum allowable slopes.

4. Using the Calculator

Tips: Enter run in feet and rise in inches. Both values must be positive numbers. The calculator will provide both the ratio format (X:1) and percentage format.

5. Frequently Asked Questions (FAQ)

Q1: What is the maximum slope ratio for ADA compliance?
A: For accessible routes, the maximum slope is 1:12 (8.33%). For shorter ramps (less than 6 inches rise), steeper slopes up to 1:8 (12.5%) may be allowed.

Q2: How do I convert ratio to percentage?
A: Divide the rise by the run and multiply by 100. For example, 1:12 ratio = (1/12) × 100 = 8.33%.

Q3: What's the difference between ratio and percentage?
A: Ratio expresses the relationship as run:rise, while percentage expresses the slope as a percentage of the horizontal distance.

Q4: When is a 12:1 ratio used?
A: A 12:1 ratio (1 inch rise per foot run) is commonly used for accessible ramps and represents the maximum slope for most public access ramps under ADA guidelines.

Q5: Can this calculator be used for roof slopes?
A: Yes, but note that roof slopes are typically expressed as rise over run (e.g., 4:12) rather than run over rise as used in ramp calculations.