Wheelchair ramp calculator

Ramp length, landings and footprint at the ADA 1:12 maximum slope.

Units

Ground to the top of the threshold.

Optional — checks whether an ADA ramp fits.

Get the materials list

ADA needs 36 in clear between the handrails.

Leave blank to skip the posts.

Deck board length

Enter the rise to see how long an ADA ramp has to be.

    How ramp length is worked out

    The ADA sets a maximum slope of 1:12. That ratio makes the arithmetic unusually easy to remember and unusually easy to underestimate: one foot of ramp for every inch you have to climb.

    ramp run (ft) = rise (in) × 1 maximum rise per run = 30 in landing = 60 in minimum, 60 × 60 in at a turn handrails = required above 6 in of rise

    Worked example: a 24 inch rise

    rise = 24 in ramp = 24 ft runs = 1 (24 in is under the 30 in limit) landings = 0 footprint = 24 ft in a straight line

    Three standard steps, and the ramp is longer than most front gardens are deep. This is why so many ramps are built as switchbacks — and a switchback adds a 60 by 60 inch turning landing to the footprint, on top of the run itself.

    What this tool will not do

    It will not solve a ramp at a steeper slope. Ratios like 2:12 and 3:12 are commonly quoted for private or unoccupied use, but they are guidance rather than a published standard, and this site does not print a physical constant no authority stands behind. If a 1:12 ramp does not fit your space, the calculator says exactly that and leaves the decision — a switchback, a different route, a lift — with you and your building department.

    Common mistakes

    • Measuring the step, not the total rise. Measure ground to threshold, including any sill.
    • Forgetting the landings. Above 30 inches of rise they are mandatory and they lengthen the footprint.
    • No level area at the top. You need somewhere flat to stop and open the door.
    • Treating 1:12 as a target. It is the steepest permitted, not the recommended.
    • Assuming a home is exempt. Some jurisdictions pull ADA-derived rules into residential code.

    What the ramp sits on

    A ramp needs a level landing at the bottom as well as the top, and that is usually a small slab — the concrete slab calculator sizes it and gives the bag count. A timber ramp on posts needs footings instead, and the post hole calculator works out the concrete around each one.

    ADA ramp length and footprint, by total rise

    RiseRamp run (ft)RunsLandingsTotal footprint (ft)
    6 in6106.0
    12 in121012.0
    18 in181018.0
    24 in241024.0
    30 in301030.0
    36 in362141.0
    48 in482153.0
    60 in602165.0

    At the ADA maximum 1:12 slope. Footprint includes 60 in landings, but not the turning space a switchback needs — a switchback landing is 60 × 60 in.

    What it takes to build

    Length is the answer people come for and not the answer they need. Open Get the materials list and give it a ramp width, and it takes off the deck, the framing and the rail. Decking runs across the ramp, so every board is one ramp-width long; stringers run with the slope at 16 in on centre; the handrail runs both sides wherever the rise is over 6 in.

    Member sizes are not here on purpose. How deep a stringer has to be over a given span is an IRC table and a question for your building department, and a figure printed here would be read as an answer to it. What is here is quantity.

    A worked ramp: 24 in of rise, 36 in wide, posts at 4 ft

    ItemBuy
    8 ft deck board20
    Stringer at 24.08 ft3
    Ft of rim board49
    Ft of handrail49
    Handrail post16

    Decking is measured on the slope, not in plan. Footings, fasteners and the landing framing are not counted — ground conditions and frost depth decide the first, and this calculator cannot see them.

    The rest of the build

    A ramp is a deck on a slope. The deck board calculator works out decking for a landing or a platform at the top, the deck footing calculator sizes the piers under it, and the board foot calculator prices framing the way a yard quotes it. Finishing it? The deck stain calculator covers the surface, and the square footage calculator handles an approach that is not a plain rectangle.

    Section through a wheelchair ramp climbing 24 inches over 24 feet, the ADA 1 in 12 maximum slope.
    Drawn to scale.

    Common questions

    How long does a wheelchair ramp need to be?

    Under the ADA the maximum slope is 1:12, which works out at one foot of ramp for every inch of rise. A 24 inch rise therefore needs 24 feet of ramp — a figure that surprises most people, because a two foot step looks like it should need a couple of yards rather than the length of a car.

    What is the maximum slope for a wheelchair ramp?

    1:12, or 8.33 percent, is the ADA maximum for new construction. That is a maximum rather than a target: gentler is easier to use, particularly for someone self-propelling, and 1:16 or 1:20 is noticeably better where the space exists. This calculator works at 1:12 because that is the compliance line.

    When does a ramp need a landing?

    Every 30 inches of rise. A single run may not climb more than that before it reaches a level landing, so a 48 inch rise means two runs and a landing between them. Landings are 60 inches long minimum, and 60 by 60 where the ramp changes direction — that turning space is what makes a switchback footprint so much larger than people plan for.

    Do I need handrails?

    Once the rise is over 6 inches, on both sides. Handrails also have their own geometry — height, extensions past the ends of the ramp, and graspable profile — which is beyond what a length calculator can tell you. Take those from the current ADA standard or your local code rather than from a rule of thumb.

    What if I do not have room for a 1:12 ramp?

    Then a compliant ramp does not fit, and this calculator will say so rather than quietly recalculating at a steeper angle. That is deliberate: steeper ratios for private residential use are widely quoted but they are guidance rather than published code, and this site does not print a number no authority stands behind. Your options are a switchback, a longer route, or a lift — and if the ramp is for a public or commercial building, non-compliance is not one of them.

    What materials do I need to build the ramp?

    Open "Get the materials list" and give it a ramp width. It takes off the decking — laid across the ramp, so each board is one ramp-width long — the stringers at 16 inches on centre running with the slope, the rim boards, the handrail down both sides, and the posts once you say how far apart you want them. Nothing is taken off until you enter a width, because the width is a decision and not something the rise implies. Member sizes and spans are deliberately absent: how deep a stringer has to be for a given span is an IRC table and a local-code question, and a figure from here would be read as an answer to it.

    How wide should a wheelchair ramp be?

    The ADA minimum is 36 inches of clear width between the handrails. That is a floor rather than a recommendation — handrails and any kerb eat into the clear width, so the framed width usually has to be wider than 36 inches to leave 36 inches clear, and 42 or 48 inches is much more comfortable for a powered chair. This calculator warns if you enter less than 36.

    Does this apply to a private home?

    The ADA governs public accommodations and commercial facilities, not private homes. Many homeowners still build to 1:12 because it is genuinely usable and because it protects resale, but a private residence is not legally bound by it. Check your local building department before assuming either way — some jurisdictions adopt ADA-derived requirements into residential code.

    Sources

    ADA sets a maximum running slope of 1:12, so one foot of run per inch of rise, and a single run may not rise more than 30 in before a landing. Steeper slopes are not simply non-compliant: the Access Board publishes two, for alterations where space is limited — 1:10 up to a 6 in rise and 1:8 up to a 3 in rise, with nothing steeper than 1:8 permitted at all. Those limits are tiny, which is the point: they exist to get over a single step, not to shorten a ramp. This calculator computes all three and labels which one it used.

    Unit conversions are exact by definition and need no source.

    How we choose and cite these figures

    By Team MaterialMath. Published . How these figures are sourced and checked.