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Ramp Slope Calculator

A ramp calculator works out how long a ramp must be for a given rise and slope — including the ADA 1:12 wheelchair standard, where every inch of height needs a foot of ramp. Enter the height to climb and pick a slope, and it gives the ramp length, the horizontal run it'll take up, and the landings required.

Your measurements

Result

People consistently underestimate ramp length: a 24 in step up at the ADA slope needs a 24 ft run. This shows that immediately, so you know whether the space fits or you need switchbacks and landings.

How it is calculated

Run = rise × slope ratio (12 for 1:12). Ramp length = √(rise² + run²). Slope percent = 100 ÷ ratio. ADA requires ≤1:12 slope, a level landing every 30 in of rise (and at top and bottom), and handrails above 6 in rise. Steeper ratios (1:8, 1:10) are only for loading or unoccupied ramps.

Steps

Measure the rise — the total height the ramp must climb.
Pick the slope (1:12 is the ADA wheelchair maximum).
Read the ramp length and the horizontal run it occupies.
Check the landings needed (one every 30 in of rise).
Add handrails for any ramp over 6 in of rise.

Worked example

A 24 in rise at the ADA 1:12 slope needs a 24 ft run — a ramp about 24.1 ft long, with one intermediate landing.

Common questions

How long should a wheelchair ramp be?

At the ADA 1:12 slope, one foot of ramp per inch of rise — so 24 in of height needs 24 ft of ramp, plus landings.

What is the ADA ramp slope?

A maximum of 1:12 (about 4.8%) for wheelchair ramps, with a level landing every 30 inches of rise and at each end.

When do I need a landing?

Every 30 inches of vertical rise, and at the top and bottom of the ramp, plus wherever it changes direction.

Can I build a steeper ramp?

Only for unoccupied loading (e.g. 1:8). For anyone using it in a wheelchair, stay at 1:12 or gentler and add handrails above 6 in rise.