calcs.homes
calcs.homes
Enter the height you need to overcome and a slope ratio to find the minimum ramp length — including whether you'll need a landing partway up.
Estimate only — full ADA compliance also requires edge protection, handrails, and specific landing dimensions.
We multiply the rise by the slope ratio's run value to get minimum ramp length — a 1:12 ratio means 12 in of ramp for every 1 in of rise. We also check whether the horizontal run passes 30 ft, or the rise passes 30 in, within one continuous run, and add the number of landings needed at whichever interval is reached first.
The 1:12 maximum slope and the 30 ft / 30 in landing intervals come directly from ADA accessibility guidelines, set to keep a ramp navigable by wheelchair users without excessive rolling force or fatigue. A landing gives a flat spot to rest, turn, or manage a door partway up a long ramp, which is why the rule is triggered by whichever limit — horizontal distance or vertical rise — comes first.
1:12 — for every inch of rise, the ramp needs at least 12 inches of run. Steeper slopes like 1:8 are only allowed for very short rises under specific exceptions.
If the ramp run exceeds 30 ft, or the rise exceeds 30 in in one continuous run, ADA guidelines require a level landing before continuing — this calculator flags that automatically.