Calculate wheelchair ramp slope, length, and cost with our free ADA ramp calculator. Check 1:12 compliance, estimate materials, and plan landings and handrails.
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A wheelchair ramp needs to hit the right slope before anything else. Get that number wrong and the ramp fails inspection, strains the person using it, or costs more than it should. This calculator takes your rise (the vertical height from ground to threshold) and either your available run or a target slope, then returns everything downstream: slope ratio, percent grade, ramp surface length, number of runs, landing count, deck area, handrail length, post count, and a full cost breakdown. Contractors use it to price jobs. Homeowners use it to check whether the space beside a door can fit a compliant ramp. It handles imperial and metric units, and all the math runs in your browser.
Pick your unit system. Choose imperial (inches, feet, square feet) or metric (millimeters, meters, square meters). Every input and result follows that choice.
Enter the total rise. Measure from the ground to the top of the threshold or landing surface. The default is 24 inches.
Choose how to set the run. Pick “Enter Run Length” if you know your horizontal distance, or “Enter Desired Slope” if you’re targeting a specific gradient.
Enter the run or slope value. If you chose run, type the horizontal distance. If you chose slope, enter the value and pick ratio, percent, or degrees.
Set the ramp width. The ADA minimum is 36 inches. Wider ramps work better for two-way traffic.
Adjust compliance settings. Set the max rise per run (30 inches by default), landing depth, handrail choice, edge protection, and post spacing.
Enter cost figures. Add decking cost per square foot, framing cost, handrail cost per foot, post cost, curb cost, labor, and any additional expenses. Leave them at zero if you just want dimensions.
Read the summary. The result panel shows slope in three formats, ADA pass/fail on slope and width, total deck area, and total cost.
The core relationship is simple: slope equals rise divided by run. Everything else builds off that. When you enter a run length, the calculator computes slope percent as (rise / run) × 100, slope ratio as run / rise, and slope degrees as atan2(rise, run) × 180 / π. When you enter a desired slope instead, the tool works backward to find the run length.
Formula: Slope percent = (Rise ÷ Run) × 100
Formula: Slope ratio = Run ÷ Rise
Formula: Slope length = √(Rise² + Run²)
Formula: Run = Rise ÷ (Slope percent ÷ 100)
The ramp surface length (also called slope length) is the hypotenuse of the triangle formed by rise and run. You need that number for decking and railing material takeoffs, not just the horizontal run.
Runs and landings depend on the max rise per run. The calculator divides total rise by that limit and rounds up. A 40-inch rise with a 30-inch max gives you two runs and three landings. Each run’s rise is the total rise divided by the run count.
Let’s run through a 27-inch rise with a 20-foot run, 42-inch width, and a target 1:12 slope check.
Inputs: Rise = 27 in, Run = 20 ft, Width = 42 in, Max rise per run = 30 in, Landing depth = 60 in.
Step 1 – Slope calculation. Convert run to inches: 20 ft × 12 = 240 in. Slope percent = (27 ÷ 240) × 100 = 11.25%. Slope ratio = 240 ÷ 27 = 1:8.89. Slope degrees = atan2(27, 240) × 180/π = 6.42°.
Step 2 – ADA check. The ADA maximum is 8.33%. At 11.25%, this ramp fails slope compliance. Width passes at 42 in. Overall: not compliant.
Step 3 – Runs and landings. 27 ÷ 30 = 0.9, rounded up to 1 run. Landings = 1 + 1 = 2. Rise per run = 27 in.
Step 4 – Surface length. Slope length = √(27² + 240²) = √(729 + 57,600) = √58,329 = 241.51 in = 20.13 ft.
Step 5 – Areas. Ramp deck area = 20.13 ft × 3.5 ft = 70.46 ft². Landing area = 2 × 5 ft × 3.5 ft = 35 ft². Total deck area = 105.46 ft².
Step 6 – Posts. Total linear length = 20.13 + 2 × 5 = 30.13 ft. With 6-ft post spacing: ceil(30.13 ÷ 6) × 2 = ceil(5.02) × 2 = 6 × 2 = 12 posts.
Interpretation: The ramp works dimensionally but exceeds ADA slope. You’d need to extend the run to at least 27 × 12 = 324 in = 27 ft to hit 1:12. That’s 7 more feet of run.
Divide the rise by the run, then multiply by 100 for percent. For a 24-inch rise over 24 feet of run (288 inches), that’s 8.33%. The calculator shows ratio, percent, and degrees at the same time so you can report the one your inspector or supplier wants.
1:12 or shallower. That’s 8.33% maximum. Anything steeper fails ADA unless the ramp qualifies for an exception, which usually applies only to existing buildings with space constraints.
At 1:12, a 30-inch rise needs 360 inches (30 feet) of horizontal run. If you want a gentler 1:16 slope, you’d need 480 inches (40 feet). The calculator figures this out when you enter a desired slope and rise.
Yes. The geometry and ADA checks work for any ramp material. Enter the concrete cost per square foot in the decking field, or use the framing cost field if you’re forming and pouring separately.
No. The run length is the horizontal distance of the sloped sections. Landings add to the total footprint but not to the slope calculation. The footprint length output shows the combined run plus intermediate landing depth.
Run is the horizontal distance from the bottom of the ramp to the top. Ramp surface length is the actual length you walk or roll along, which is the hypotenuse. A 24-inch rise with a 24-foot run has a surface length of about 24.05 feet.
The calculator estimates posts by dividing the total linear length (slope length plus landing depths) by your post spacing, then multiplying by two for both sides. A 30-foot total with 6-foot spacing gives 10 posts. It adds two more posts per intermediate landing.
The tool flags it as not compliant. You’ll need to extend the run, add a switchback with a landing, or reduce the rise. The calculator shows the slope percentage so you can see how far over you are.
Yes. It runs in your browser, there’s no signup, and you can use it as many times as you want. No data gets sent anywhere.
Enter your material and labor costs in the cost section. The calculator divides total cost by total deck area to give you a cost-per-square-foot figure. That number helps when you’re comparing bids from different contractors.
Permit rules vary by location and by whether the ramp is permanent or temporary. Most jurisdictions require a permit for a permanent ramp attached to a structure. Check with your local building department before you start.
Edge protection is a curb or barrier at least 2 inches high along the sides of the ramp and landings. It stops wheels from rolling off the edge. The calculator includes it as a separate cost line and length calculation.
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