HesapHanem

Wheelchair Ramp Calculator

Find ramp length and slope.

How it is calculated

The ramp is treated as a right triangle. The rise is the vertical height in centimetres and the ratio 1:N means N units of horizontal distance for every 1 unit of rise. So run = rise × N, length = √(rise² + run²) and angle = atan(rise ÷ run). Run and length are reported in metres (run to one decimal, length to two) and the angle in degrees. If the ratio is left empty, zero or negative, the tool falls back to 12, i.e. a 1:12 slope. The rise must be above zero. Only the sloped surface is calculated: landings, handrails, width and edge protection are not included. The slope limits for accessibility vary by country and by building type, so check the rule that applies to your project; the tool does not know which one that is.

Worked example

A threshold 45 cm high with a 1:12 slope. Run = 45 × 12 = 540 cm = 5.4 m. Ramp length (the sloped surface) = √(45² + 540²) = √293,625 ≈ 541.87 cm = 5.42 m. Angle = atan(45 ÷ 540) = 4.76 °. So the horizontal distance needed is 5.4 m, the ramp board itself is a little over 5.4 m long, and it rises at under 5 degrees. A steeper 1:8 ratio on the same rise would shorten the run to 3.6 m but raise the angle to 7.13 degrees.

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Common mistakes

  • Entering the rise in metres or inches. The field is in centimetres, so 0.45 is read as 0.45 cm and gives a ramp only a few millimetres tall.
  • Entering the slope as an angle or percentage. The ratio is the N in 1:N, so 12 means 1:12; a 12-degree ramp is much steeper than 1:12.
  • Using the run as the board length. The run is the horizontal distance; the sloped surface is slightly longer, which is the Length figure.
  • Leaving the ratio at 0 expecting a flat result. A zero or negative ratio is silently replaced by 12.
  • Applying one rise to a ramp that has landings. A long ramp usually needs flat platforms, and each section has its own rise, so calculate them one at a time.

About this calculator

This calculator finds the ramp length and angle needed for a given rise (vertical height) and slope ratio, using basic right-triangle trigonometry. The ADA recommends a maximum slope of 1:12 for wheelchair ramps, meaning 1 inch of rise for every 12 inches of ramp length, though gentler slopes are easier to use.

Contractors and homeowners use it to plan a compliant ramp before building, and caregivers use it to check whether an existing or planned ramp will be safe and usable.

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Comments (1)

  • Editorial team

    Check the total rise before you trust one long answer. Under US ADA standards a single ramp run may climb no more than 30 inches, about 76 cm, before it needs a level landing. Entering 76 cm at 1:12 gives a run of 9.1 m, so a taller rise has to be split into runs with landings between them, each calculated separately. Rules differ elsewhere, so confirm yours. What rise are you dealing with, and how much space do you have?

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