How to Measure for a Wheelchair Ramp: Rise, Length and Landings

The most common ramp mistake is buying or building one that is simply too short. A ramp that looks reasonable in the driveway can be dangerously steep for someone pushing a manual chair or for a caregiver guiding a heavy power chair downhill. Learning how to measure for a wheelchair ramp correctly comes down to a few careful numbers: total rise, slope, run length, landings and width. Get those right on paper and every later decision, from aluminum modular kits to a custom wood build, becomes straightforward.

How to Measure for a Wheelchair Ramp: Start With Total Rise

Everything starts with rise, the vertical distance from the ground where the ramp will end to the top surface where it will begin, usually the door threshold or porch floor. Measure it accurately, because every inch of rise adds about a foot of ramp at the standard slope.

1. Place a straight board or long level on the threshold, extending it out past the steps so it is perfectly level.
2. Measure straight down from the underside of the board to the ground with a tape measure. That number is a first estimate of rise.
3. Account for sloping ground. Yards and driveways rarely sit flat. Because the ramp will end several feet away, the ground at that spot may be higher or lower than at the base of the steps. For an accurate figure, extend a level line (a string line with a line level, or a laser level) out to where the ramp will likely touch down and measure there.
4. Measure more than once. Write down the rise to the nearest quarter inch. Round up, not down, when in doubt.

Do not forget the door threshold itself. A raised sill of an inch or so can be a real barrier and may need a small threshold ramp or a replacement sill in addition to the main ramp.

Apply the Slope: The 1:12 Rule

The ADA Standards for Accessible Design set a maximum running slope of 1:12 for ramps, meaning 1 inch of rise for every 12 inches of run, or 1 foot of ramp length for every inch of rise. Private homes are not always legally bound by ADA, but the 1:12 figure is the widely accepted benchmark, and many local codes use it or something similar.

The math is simple: rise in inches = minimum ramp run in feet.

• 6-inch rise = at least 6 feet of ramp
• 18-inch rise = at least 18 feet of ramp
• 24-inch rise = at least 24 feet of ramp
• 30-inch rise = at least 30 feet of ramp

1:12 is a maximum, not a target. Many wheelchair users, especially those self-propelling or with limited upper-body strength, find a gentler slope far easier. A 1:16 or 1:20 slope needs a longer ramp but can be the difference between independent use and needing help. Scooter and power chair users may tolerate steeper slopes for short temporary setups, but manufacturer guidance and the user’s comfort should decide that, not the available yard space.

Plan Landings and Maximum Run Lengths

Long ramps need resting points. Under the ADA standard, a single ramp run can rise no more than 30 inches before a landing is required. At 1:12, that works out to a 30-foot run.

Landing dimensions matter just as much as ramp length:

• Top and bottom landings: at least 60 inches long, and at least as wide as the ramp run leading to them.
• Intermediate landings: at least 60 inches long between runs.
• Turning landings: where the ramp changes direction, the landing should be at least 60 by 60 inches so a wheelchair can turn.
• Door landings: the top landing must leave room to open the door without rolling backward. Extra maneuvering space on the latch side of the door is important, particularly when the door swings outward toward the ramp.

When calculating total footprint, add each landing to the run length. For example, a 36-inch rise at 1:12 needs 36 feet of ramp. Split into two 18-foot runs with a 5-foot intermediate landing and a 5-foot top landing, the overall layout covers about 46 feet of travel, plus a clear flat area at the bottom.

Choose a Layout That Fits Your Site

Once you know total run and landing count, sketch the site to scale on graph paper. Measure the distance from the door to the driveway, sidewalk or parking spot, and note obstacles such as trees, windows, downspouts, utility meters and property lines.

Common Layouts

• Straight run: simplest to build and use, but needs the most linear space.
• L-shape: one 90-degree turn on a 60×60-inch landing; fits along the side of a house.
• Switchback (U-shape): two runs doubling back on each other via a turning landing; compact footprint for higher rises.

Plan where the ramp ends, too. The bottom should land on a firm, level, slip-resistant surface such as a concrete walk or driveway, with a clear flat area at least 60 inches long so the user can stop and turn safely.

Width, Handrails and Edge Protection

Length gets most of the attention, but width and railings determine whether a ramp feels safe.

• Clear width: the ADA minimum is 36 inches between handrails. Many residential users prefer 42 to 48 inches, especially for power chairs or when a caregiver walks alongside.
• Handrails: required under ADA when a ramp run rises more than 6 inches. Rails go on both sides, with the top of the gripping surface between 34 and 38 inches above the ramp surface, and should extend 12 inches beyond the top and bottom of each run.
• Edge protection: a curb or barrier along open sides keeps wheels and casters from slipping off the edge. A raised curb of at least a few inches or a rail placed low enough to stop a wheel is typical.
• Surface: slip-resistant in wet conditions. Grit tape, textured aluminum, or a broom finish on concrete all work. Keep cross slope minimal so the chair does not drift sideways.

Measuring for Modular, Portable and Custom Ramps

Different ramp types use your measurements differently.

Portable and threshold ramps handle small rises, such as a single step or a raised sill. Measure the rise and the depth available in front of the door. Manufacturers list recommended rise for each length; because portable ramps are often used steeper than 1:12, pay attention to whether the user will self-propel or be assisted.

Modular aluminum ramps come in sections and platforms sized to standard lengths. Give the dealer your exact rise, a site sketch, door swing direction, and preferred width. Many suppliers will send someone to measure, which is worth accepting.

Custom wood or concrete ramps are built to your plan and usually require a building permit, footings and inspections. Local setbacks may limit how close to the property line a ramp can be.

Common Measuring Mistakes to Avoid

• Measuring from the top step instead of the threshold. Always measure to the actual surface the chair must reach.
• Ignoring ground slope. A yard that falls away adds rise; one that climbs reduces it.
• Forgetting landings. Leaving out the top landing is the most frequent planning error, and it forces the user to open the door while on a slope.
• Choosing width by chair width alone. Leave room for hands on the push rims and elbows.
• Not planning for change. A user who walks with a cane today may need a power chair later. Designing for the more demanding case avoids rebuilding.

Get Expert Input Before You Build

Measurements are only part of the picture. An occupational therapist (OT) can assess the user’s strength, chair type and daily routine, and recommend a slope, width and layout that truly works for them. A Certified Aging-in-Place Specialist (CAPS) contractor or an experienced accessibility installer can translate that plan into a structure that meets local code. For ramps attached to the house, built on footings, or rising more than a couple of feet, a licensed contractor and a permit are strongly recommended; structural connections to decks and porches must carry real loads. Some nonprofits, veterans programs and local agencies offer ramp assistance, but eligibility and funding vary widely, so contact them directly to learn what, if anything, applies to your situation.