In ADA ramp design, what does a slope of 1:12 indicate?

• A. 12 inches vertical for 1 inch horizontal
• B. 1 inch vertical for every 12 inches horizontal
• C. 6 inches vertical for every 1 inch horizontal
• D. 1 inch vertical for every 6 inches horizontal

Answer: (D)

The key idea is how to read the ratio as rise over run. A slope of 1:12 means you gain 1 inch of vertical height for every 12 inches of horizontal travel. In other words, for each foot you move forward, you rise about 1 inch, which is about an 8.3% grade. This is the standard maximum slope used in ADA ramp design to keep ramps accessible for wheelchairs. If you need to rise more than a small amount, you must add landings to keep each section within that 1:12 limit. For example, a 6-inch rise requires 72 inches (6 feet) of ramp run. The other options describe steeper or different ratios that do not match the 1:12 standard.