A ramp is set by its slope: the horizontal run needed for each inch of rise. At the steepest slope the ADA standards allow, every inch of rise needs 12 inches of run. Each run may rise only so far before it levels off, so a tall ramp needs landings, and those add length. The calculator counts them, so you can see the space before you buy materials.
How to use this calculator
- Measure the total rise from where the ramp will land up to the finished floor or threshold. Enter it in inches, feet, centimeters or meters.
- Start with the steepest slope, the top option in the Slope menu, which allows a run of 12 inches for every inch of rise. Choose a gentler option when the space allows, since it is easier to climb.
- Read the ramp run and the surface length. The run is the horizontal distance, and the surface length is the diagonal you roll or walk on.
- Check the straight length. When landings sit between runs, it includes them, so measure the space with that number rather than the ramp run alone.
- Plan a level landing at least 60 inches long at the top and bottom, a turn landing at least 60 inches square wherever the ramp changes direction, and a clear width of at least 36 inches. Then estimate the framing with the board feet calculator.
Worked examples
Front door step
Total rise: 7 in
- Ramp run
- 7.0 ft
- Sloped runs
- 1
- Landings between runs
- 0
- Slope
- 8.33%
- Angle
- 4.8°
Front porch on a gentler slope
Total rise: 18 in · Slope: 1:16
- Ramp run
- 24.0 ft
- Sloped runs
- 1
- Landings between runs
- 0
- Slope
- 6.25%
- Angle
- 3.6°
Back deck
Total rise: 3 ft
- Ramp run
- 36.0 ft
- Sloped runs
- 2
- Landings between runs
- 1
- Straight length with those landings
- 41.0 ft
- Slope
- 8.33%
- Angle
- 4.8°
Garage side door
Total rise: 4 in
- Ramp run
- 4.0 ft
- Sloped runs
- 1
- Landings between runs
- 0
- Slope
- 8.33%
- Angle
- 4.8°
Ramp run for common rises and slopes
| Total rise | Slope: 1:12 | Slope: 1:16 | Slope: 1:20 |
|---|---|---|---|
| 6 in | 6.0 | 8.0 | 10.0 |
| 12 in | 12.0 | 16.0 | 20.0 |
| 24 in | 24.0 | 32.0 | 40.0 |
| 36 in | 36.0 | 48.0 | 60.0 |
Each cell: Ramp run (ft). Inputs not in the table use the calculator's starting values.
Measuring the rise
Measure from the surface where the bottom of the ramp will sit, usually the ground or a lower slab, up to the finished floor or top of the threshold. Include any decking, sill or mat above the framing, since the ramp must reach the finished height.
If the ground slopes, measure at the exact spot where the bottom will stand, and make sure that spot is firm and level. A low starting spot adds rise you did not count, so measure again once the grade is final.
Slope, scope and gentler ramps
The ADA standards apply to public and commercial buildings. A private home usually falls under the local residential code, which can differ from the ADA figures. Many homeowners still use the ADA numbers as the safe target for their own ramp.
Gentler slopes are easier for someone pushing themselves or for a helper, but they need more room at the bottom. Choose the steepest slope only when the space is tight. If a deck also needs steps for visitors, work those out with the deck step calculator.
Landings, turns and layouts
A run may rise no more than 30 inches, so a taller ramp is split into runs with a landing between them. Each landing is at least 60 inches long, and the calculator adds those in-between landings to the straight length. It does not add the landings at the top and bottom, so leave room for those separately.
A switchback turns the ramp back on itself, and an L-shaped layout turns a corner. Either way, the landing at the turn must be at least 60 inches square. A switchback folds the straight length into a shorter footprint, but it needs width for both runs. A porch with steps beside its ramp needs the stair calculator for the steps, since this calculator sizes only the ramp.
Handrails and common mistakes
A run that rises more than 6 inches needs a handrail on both sides, set at 34 to 38 inches above the surface and extended 12 inches past the top and bottom of each run. The calculator flags whether a ramp needs handrails, but it does not lay them out.
The calculator does not cover edge protection, the curb or guard along an open side. Ask your building department what the local rule requires.
- Measuring to the framing or subfloor instead of the finished floor, so the ramp ends short of the threshold.
- Mixing up the ramp run and the surface length. The run is horizontal, and the surface length is longer.
- Skipping the top or bottom landing. The door swing needs room on that landing too.
Is this a wheelchair ramp calculator or a car ramp calculator?
This calculator sizes access ramps to a door, porch or deck, such as a wheelchair, walker or stroller ramp. It is not for vehicle, loading or trailer ramps, which follow different rules.
Common questions
How steep can a wheelchair ramp be?
The steepest slope the ADA standards allow is a run of 12 inches for every inch of rise. Gentler slopes are easier to climb, so use the steepest one only when the space leaves no other choice. Local rules for a home ramp can differ.
How do I work out the length of a ramp?
Multiply the total rise by the slope ratio to get the ramp run. Then add the landings between runs to get the straight length the layout needs.
Does a ramp need handrails?
A run that rises more than 6 inches needs a handrail on both sides under the ADA standards, set at 34 to 38 inches above the surface. Check local rules for a home ramp, since they can differ.
Do I need a permit for a ramp?
That depends on your local rules and the size of the job. Ask your local building department before you start, because the calculator does not decide whether a permit applies.
What is the cross slope of a ramp?
Cross slope is the side-to-side tilt of a ramp run, across its width. Keep it no steeper than one to 48: the surface may drop one unit for every 48 units of width, so the ramp does not push a wheelchair sideways. The calculator does not check cross slope, so level the surface as you build.