How Steep Is Too Steep for a Home Ramp? The ADA 1:12 Rule Explained
A ramp is a trade between how high you must climb and how far you must travel to climb it. The 2010 ADA Standards, published by the U.S. Access Board, pin that trade down with a number: a ramp run should have a running slope not steeper than 1:12. The ADA covers public and commercial buildings and does not bind a private home, but it is the clearest published rule for how steep a ramp should be.
What 1:12 Means in Inches
A slope of 1:12 means that for every 1 inch of rise, the ramp is 12 inches long. Multiply the rise by 12 to get the length.
| Step height | Ramp length at 1:12 |
|---|---|
| 2 inches | 24 inches (2 feet) |
| 3 inches | 36 inches (3 feet) |
| 6 inches | 72 inches (6 feet) |
| 8 inches | 96 inches (8 feet) |
| 12 inches | 144 inches (12 feet) |
Our ramp length calculator does the multiplication and lists the portable ramps in our guide that are long enough.
When Steeper Is Allowed
For existing sites where space is limited, the ADA allows steeper slopes, but only for small rises. A slope steeper than 1:12 up to 1:10 is allowed for a rise of 6 inches or less, and a slope steeper than 1:10 up to 1:8 for a rise of 3 inches or less. Anything steeper than 1:8 is prohibited. The cross slope, the tilt from side to side, should not be steeper than 1:48.
The Other ADA Numbers
- Rise per run: 30 inches at most. A higher step needs landings and more than one run.
- Landings: 60 inches long at the top and bottom, and 60 by 60 inches where the ramp changes direction.
- Clear width: 36 inches minimum. The portable ramps in our guide are about 29 inches wide.
- Handrails: required on ramp runs with a rise greater than 6 inches.
- Edges: edge protection on each side of the ramp and landings.
What the Listings Say
The Amazon listings for portable ramps give step heights that are much steeper than 1:12. The VNN 3-foot ramp lists 3 to 9 inches, which at its 36-inch length is as steep as 1:4. The VNN 6-foot lists 6 to 18 inches and the WHALEMOTOR 8-foot lists 8 to 24 inches, also reaching 1:4. A ramp that steep is hard to push a chair up and easy to tip, and it is outside what the ADA allows. Use the 1:12 rule to choose the length, and treat the listing's range as an outer limit.
Check your chair too. A ramp that is steeper than you can push is not a solution, even if the listing says it will take the load. A physical therapist or occupational therapist can say how steep a slope you or a helper can manage.
Which Ramp for Which Step
For a 2 or 3 inch threshold, a 2 or 3 foot portable ramp matches the rule. For a 6-inch porch step, you need about 6 feet, and for 8 inches about 8 feet. Above 6 inches, the ADA also asks for handrails, which portable ramps do not have. Our wheelchair ramp guide compares five ramps from 2 to 8 feet.
