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Use our free Ramp Slope Ratio Calculator to instantly compute ramp grade, percentage, and angle. ADA compliant, precise, and easy to use for ramp planning.
If you're planning to build a ramp for a home, business, or public space, getting the slope right is extremely important. Whether it's for wheelchair access, carts, or general walkways, the ramp should be safe and comfortable to use. That’s why we created the Ramp Slope Ratio Calculator — a simple tool to help you find the exact slope ratio, percentage, and angle based on your ramp’s rise and run.
Ramp slope ratio is the relationship between the vertical rise (height) and the horizontal run (length) of a ramp. It tells you how steep or gentle the ramp is.
A common example is a 1:12 slope ratio, which means for every 1 inch of rise, there are 12 inches of run. This is the standard recommended by the ADA (Americans with Disabilities Act) for wheelchair ramps. It's designed to ensure safety and comfort for all users.
The slope ratio is calculated using a very simple formula:
Slope Ratio = Rise / Run
To express it in the traditional format like 1:12, you take the slope and invert it:
Slope Ratio Format = 1 : (Run / Rise)
For example, if your ramp rises 20 inches and runs 240 inches, the ratio would be:
Slope = 20 / 240 = 0.0833
Ratio Format = 1 : (1 / 0.0833) = 1 : 12
You can also convert the slope into percentage and angle:
Slope Percentage = (Rise / Run) × 100
Slope Angle (Degrees) = arctangent (Rise / Run)
These calculations are automatically handled by our Ramp Slope Ratio Calculator.
A 1:12 ratio ramp means for every 1 unit of vertical rise, there are 12 units of horizontal run. This ratio is considered the standard for accessibility ramps in most countries, including the U.S.
So, if your rise is 24 inches, your ramp should be at least:
24 inches × 12 = 288 inches (24 feet) long
This ensures the ramp is not too steep and can be safely used by wheelchairs, walkers, and even people pushing strollers or carts.
To calculate ramp length, simply multiply the rise by the slope ratio. Using the standard 1:12 ratio:
Ramp Length = Rise × 12
Ramp Length = 20 inches × 12 = 240 inches (20 feet)
So, for a 20-inch rise, you need a ramp that's at least 20 feet long for safe and ADA-compliant use.
The most accepted standard slope for accessibility ramps is 1:12, which equals about 8.33% slope or approximately 4.76 degrees.
Other guidelines:
The tool will instantly show you:
If your ramp slope exceeds safe limits, it will display a warning or danger message.
Whether you're designing a wheelchair ramp, garden path, driveway, or any sloped surface, knowing the correct slope ratio is essential for safety and comfort. Our Ramp Slope Ratio Calculator takes the guesswork out and gives you instant, accurate results with ADA compliance checks.
You don’t need to be a math expert — just input your values and get your result. This tool is perfect for engineers, architects, contractors, DIY builders, and anyone working on accessibility features.
The ADA recommends a maximum slope of 1:12, which is equal to 8.33% or 4.76°.
For short ramps, yes — but it’s not considered ADA-compliant for standard wheelchair access.
Yes! You can input values in meters, centimeters, or millimeters. The tool automatically converts them to perform accurate calculations.