How to Measure for a Wheelchair Ramp (and What Length You Need)

How long should a wheelchair ramp be?

Ramp length is driven primarily by one number: your rise: the total vertical height you need to climb, from the lower ground to the top of the doorway threshold or landing. At the ADA 1:12 slope, you multiply that rise by 12 to get the minimum ramp length.

A useful shortcut falls out of the 1:12 ratio: at 1:12, your minimum ramp length in feet is the same number as your rise in inches. A 6-inch rise wants 6 feet of ramp; a 30-inch rise wants 30 feet.

These are minimum lengths at the recommended 1:12 slope. A slightly longer ramp is gentler and easier to push, so if you have room, err long rather than short. The ramp length calculator also shows the shorter lengths for assisted (1:6) and unoccupied (1:4) use (see the slope section below for when each is safe), and flags when your rise crosses the 30-inch single-run limit and needs a landing.

Which type of ramp fits your rise. Length is only half the answer. The rise also decides the kind of ramp you need. A door sill or single low threshold is threshold-ramp territory, like the SafePath EZEdge rubber threshold ramp. One or two steps usually calls for a portable ramp that folds down for storage and travel, such as the PVI multifold portable ramp. A raised porch, or any rise past a couple of feet, is where modular systems come in: the Rampit USA 36-inch aluminum modular ramp builds in sections and can incorporate the landings a taller rise requires. Always check a product's rated rise and weight capacity against your own measurements before ordering.

Wheelchair ramp slope explained

Slope is the relationship between rise and length, written as a ratio like 1:12, read as "1 inch of rise for every 12 inches of ramp." The same slope can also be written as a percentage grade or an angle in degrees, and you'll see all three on product pages and in the calculator above.

For a portable wheelchair ramp there are three slopes worth knowing, and they're exactly the three the calculator gives you. Each trades length for steepness, and each has one safe use:

Read a ratio as rise to length: 1:12 means every inch of rise needs 12 inches of ramp, while 1:4 needs only 4, so the smaller the second number, the steeper the climb. Whenever you have the room, choose 1:12 or gentler (a 1:16 or 1:20 slope is easier still), because a longer ramp is always safer, and the most common sizing mistake is buying a ramp that turned out too short. Always follow your wheelchair or scooter's owner manual, which may set its own maximum slope.

You may see the two steeper slopes written elsewhere as 2:12 and 3:12. Those are the same inclines in unreduced form: 2:12 is 1:6, and 3:12 is 1:4.

Permanent vs. Portable: don't mix them up. The 1:6 and 1:4 slopes above are portable-ramp guidance for assisted or unoccupied use; they are not ADA-compliant. A permanent ramp on an accessible route must meet the ADA 1:12 maximum, and the only steeper ADA allowances are narrow existing-site exceptions (up to 1:10 for a rise of 6 in or less, up to 1:8 for a rise of 3 in or less). Building a fixed ramp for a business or public building? Size it to 1:12.

Rise and run: what the two numbers mean

Every ramp calculation comes down to two measurements:

• Rise. The vertical height the ramp has to climb. Measure straight up from the lower surface to the top surface (threshold, porch, or landing). This is the number the calculator asks for.
• Run. The horizontal distance the ramp covers along the ground. The run is the flat "footprint" the ramp occupies, which is not the same as the ramp's own length, though at shallow ADA slopes the two are very close.

Slope is simply rise ÷ run. Fix the slope at the ADA 1:12 maximum and the run (and therefore the length) is decided for you by the rise, which is why the calculator only needs one input to start.

How to measure for a wheelchair ramp

Getting the rise right is the whole job. Take five minutes and do it carefully:

1. Measure the total rise. Rest a straight board or level on the top surface (the threshold or porch edge) so it extends out over the lower ground. Measure vertically from the bottom of that board down to the lower ground. That vertical distance is your rise, not the diagonal.
2. Measure from the true bottom. If the ground slopes away or there's a bottom step, measure to where the ramp will actually land, not to the base of the wall.
3. Check the top surface. You need a firm, level area at the top wide enough to turn and to clear the door swing. A door that swings outward over the ramp usually needs a level landing in front of it.
4. Confirm you have horizontal room. Multiply your rise (in inches) by 12 to get the minimum length in inches, and make sure that distance fits your walkway, driveway, or yard before you buy.
5. Enter the rise in the calculator. The ramp length calculator returns the minimum horizontal run at a 1:12 slope.

When you need a landing or more than one ramp

A single ramp run can climb a maximum of 30 inches of rise before a level landing is required, which at 1:12 is a 30-foot run. For anything taller, the ramp is built as multiple runs connected by landings rather than one continuous slope.

Level landings are required at the top and bottom of each ramp run. A straight landing must be at least as wide as the ramp and 60 inches long. Where the ramp changes direction, the landing must provide at least 60 by 60 inches of clear space. You also need a landing at the top and bottom of every ramp and at any change in direction. A switchback around a raised porch, for example, needs a landing at each turn. There's no ADA cap on a system's total length across multiple runs, but longer ramps are more tiring, so shorter routes with landings beat one very long slope.

Does a home ramp have to follow the ADA rules?

The ADA is a legal standard for businesses and public accommodations; a private home is not legally required to meet it. But the 1:12 slope isn't red tape. It's the point at which most people can use a ramp safely and independently, so it's the right target for a home ramp too whenever space allows.

Where a yard genuinely can't fit a full-length ramp, the steeper portable slopes above can shorten it, but only within their limits: 1:6 only with a capable helper and an occupied chair, 1:4 only when no one is riding. Someone self-propelling a manual wheelchair on their own should stay at 1:12 or gentler. If you're unsure, size to 1:12, or measure your rise and talk it through with us before you buy.

General advice notice. This guide and the calculator provide general educational information, not a professional site assessment, engineering opinion, or legal determination of ADA compliance. Requirements can vary with your specific site and with state or local building codes, which are sometimes stricter than the federal ADA Standards. Verify any regulatory requirement against current ADA / U.S. Access Board sources and your local code before purchasing or installing.