How this calculator works
Slope is rise divided by horizontal run. Sloped ramp length is the hypotenuse, so it is longer than the run. Splitting a ramp gives two equal sloped segments but does not add the landing space. Under US ADA guidance, a new accessible ramp generally has a maximum running slope of 1:12 and a maximum rise of 30 in per run. Those rules alone do not establish full compliance; Canadian requirements depend on the applicable jurisdiction.
Formula
run = rise x ratio denominator; grade = rise/run; angle = atan(grade); sloped length = sqrt(run² + rise²).
Worked example
A 0.5 m rise at 1:12 needs 6 m horizontal run and 6.021 m of sloped surface. A 3 m rise over 4 m run has a 5 m slope and a 75% grade.
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Frequently asked questions
Is 1:12 the same as 12%?
No. One divided by twelve is 0.08333, or about 8.33%.
Are steep loading ratios accessible?
The 1:6 and 1:4 choices are geometry scenarios only. They are not accessible-ramp recommendations.
What else does a ramp need?
Check landings, run limits, cross slope, clear width, edge protection, handrails and local rules before building.