Wheelchair Ramp Calculatorby AccessProof

Ramp guide

How to measure for a wheelchair ramp

The rise you measure decides everything downstream: how long the ramp has to be, how many landings it needs and what it will cost. Here is how to measure the route, where to put the tape, and the three numbers to write down for every doorway.

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A wheelchair ramp is sized from one number: the rise, the total vertical distance the ramp has to climb. Get that number right and everything downstream, the run length, the landings, the quote, falls into place. Measuring is not hard work, but it is worth doing properly: the trick is measuring the whole route, not just the step in front of you.

The route, not the step

The rise is the vertical distance between the lowest surface someone will travel from and the highest surface the ramp delivers them to. For a typical home entrance that means from the street, driveway or walkway at the bottom up to the porch, deck or interior floor at the top.

Two mistakes are common. The first is measuring only the steps: the lowest point of the route is often not at the base of the stairs. If the walk slopes down toward the street, or a curb sits between the parking spot and the door, the route starts lower than the steps suggest. The second is measuring to the top step instead of the top surface. The ramp has to reach the floor the wheelchair will roll onto, and that surface is the top of the rise.

The measurement itself is the same one the requirements guide describes: hold the tape vertically between the two finished surfaces at the actual ramp location. A level and a tape measure work, and so does a straight edge with a string line. Do not measure the diagonal length of the slope, and do not multiply steps blind: riser heights vary, and the IRC caps residential risers at 7¾ inches, so 12 steps is roughly 84 to 93 inches of rise. Measure, do not assume.

Where to put the tape

Walk the route the wheelchair will take, front to back, and let the tape sit at each place the surface changes height:

  • Street or gutter: often the true lowest point. Measure the surface the wheelchair will actually cross, not the one beside it.
  • Driveway apron or curb: any curb along the route changes the height before the ramp even starts. If the route crosses a driveway apron or a curb, that is where the rise begins.
  • Walkway or stoop: the flat area at the bottom of the steps, where the ramp will actually land. Check whether it slopes; a sloped bottom changes the effective rise.
  • Door lip or threshold: a raised saddle or a sliding door track adds to the top of the route. A couple of inches at the door can be handled by a threshold ramp of its own, but include it in the numbers unless you plan to bridge it that way.
  • Porch, deck or floor: the top finished surface, measured at the point where the ramp will arrive.

Plan the landing space while you are out there

The rise decides the ramp run, but the landings decide whether the ramp fits. Under the ADA a landing is required at the top and bottom of every run (§405.7), at least 60 inches (1525 mm) clear in the direction of travel (§405.7.3) and at least as wide as the run (§405.7.2). Where the ramp turns between runs, the landing grows to 60 × 60 inches (§405.7.4).

The doorway is where this bites. Where a door opens onto or beside a landing, the door's maneuvering clearance may extend into the landing area (§405.7.5), so the clear space has to sit outside the swing of the door, screen door included. Open the door all the way, mark where the swing ends, and measure from there to the edge of the porch or deck. If that leaves less than 5 feet, the top landing is the constraint your design has to solve, not an afterthought.

At the bottom, the same idea in reverse: the ramp ends in a landing of its own, so the bottom needs clear flat space where a chair can stop and turn, not just the last few inches of pavement.

Three numbers per doorway

For every doorway you plan to serve, write down three numbers:

  1. Rise, in inches: the lowest to highest finished surface, measured vertically. Inches or centimeters both work.
  2. Run available, in feet and inches: the horizontal distance you can actually build along. Measure the route you would really use, and split it into segments where the ramp would turn; a 40-foot yard is not 40 feet of ramp if the path turns twice.
  3. Clear landing depth, in inches: at the top, from the door swing to the outer edge of the landing area; at the bottom, the flat space where the ramp lands.

An entry might read: "Front door: rise 22 in; run available 26 ft; top landing 42 in clear, bottom 36 in." Repeat it at the side door and the garage door even if you expect one entrance is enough; the numbers often change the plan. The plan will not use the full width of everything you measure, so keep the raw numbers rather than rounding them up on site.

From measurements to a plan

  1. Take each rise to the ramp calculator. It returns the run length at your chosen slope, how the rise splits into runs, the landing count and sizes, whether handrails are required, and a printable spec sheet.
  2. Compare the required run with the run you measured. If a straight layout does not fit, the plan changes shape, not physics: a switchback doubles part of the route back on itself and needs a 60 × 60 inch turning landing, which changes where the ramp sits on the site.
  3. Price the result with the cost estimator, which also takes handrails and install type into account.
  4. For the construction details, the landings and handrails guide covers sizes, door swing overlap and what the residential code asks for.

Measure the route twice, write the three numbers down for every doorway you might use, and the rest of the project turns into arithmetic. The rise goes in; the plan comes out.

Sources

All links checked October 17, 2026. This is general information, not design or engineering advice. Measure carefully, and confirm your design and permits with your local code authority.