Calculators/ Framing & Exterior/Ramp Slope Calculator
Ramp Slope Calculator
Ramp length, slope and landings for a given rise.
Ramp Slope Calculator
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Accessible ramps are governed by slope, not by length. The ADA maximum of 1:12 means a foot of ramp for every inch of rise, which surprises people: a two foot rise needs a twenty-four foot ramp plus landings.
How this is calculated
- Ramp run = rise × the slope ratio. At 1:12, a 24 inch rise needs 288 inches, or 24 feet of ramp.
- The ADA limits a single run to 30 inches of rise. Beyond that, a level landing at least 60 inches long is required between runs.
- Gentler slopes are easier to use unaided. At 1:20 or flatter, handrails are not required by ADA.
Frequently asked questions
What is the maximum ADA ramp slope?
1:12, or 8.33%. Steeper ramps are sometimes permitted in alterations to existing buildings where space is genuinely constrained, but not in new construction.
When do I need a landing?
At the top and bottom of every ramp, and between runs whenever the rise exceeds 30 inches. Landings must be at least 60 inches long and as wide as the ramp.