Ramp Calculator

Plan ramp length from rise, slope, and space

This ramp calculator estimates the horizontal run and sloped length needed to bridge a vertical rise. Enter the rise, choose a slope ratio, and set the clear ramp width, landing depth, and maximum rise per run for your planning scenario. The calculator shows the incline angle, percent grade, number of ramp runs, landing count, surface area, and total footprint including landings.

A ramp with a 1:12 slope rises one unit for every twelve horizontal units. A 24-inch rise at this ratio needs 24 feet of horizontal run, before adding level landings. A flatter slope needs a longer run but feels less steep. If space is limited, do not simply choose a steeper ratio without checking the applicable accessibility rules, site conditions, and any approved exceptions.

This is a planning calculator, not a code-compliance check or a structural design. Accessibility standards specify more than ramp length: clear width, cross slope, landings, handrails, edge protection, surface, drainage, and route connections can all matter. Requirements depend on location, building type, use, and project scope. Confirm the design with the authority having jurisdiction and a qualified accessibility or building professional.

How to use the accessible ramp calculator

Choose inches or millimetres for the vertical rise, ramp width, landing depth, and maximum rise per run. The slope ratio is horizontal distance divided by vertical rise. Select a common preset or choose custom and enter your own ratio. For example, a ratio of 12 means twelve inches of horizontal run for every inch of rise. Use the same physical units for all dimensions in the selected mode.

Enter the clear width available for travel. Where handrails are planned, the clear width may be measured between the handrails rather than from outside edge to outside edge. Enter the landing length you want to include at the top, bottom, and intermediate turns. The calculator uses one repeated landing dimension to estimate overall footprint and area. Real projects may have different top, bottom, and turning landing sizes.

Set the maximum rise allowed for each ramp run. The calculator divides the total rise into enough segments to stay at or below this input, then adds a landing at the top and bottom and between adjacent runs. The common reference value of 30 inches (760 mm) is drawn from the 2010 ADA Standards for many ramp runs, but different applications can have different requirements. Confirm the standard that applies to your project.

Ramp slope, run, and length formula

The slope ratio is a rise-to-run relationship expressed as 1:n. The horizontal run equals the vertical rise multiplied by n. The sloped surface length is the hypotenuse of a right triangle, so it is calculated from the square root of rise squared plus run squared. The angle from level ground is the arctangent of rise divided by run. Percent grade is rise divided by run, multiplied by 100.

For example, a 1:12 slope has an 8.33 percent grade and an angle of about 4.76 degrees. A 30-inch rise at 1:12 needs 360 inches, or 30 feet, of horizontal run. The sloped length is slightly longer than the horizontal run. Landings add level area to the footprint but are not included in the ramp run length.

If total rise exceeds the maximum rise per run, the calculator splits it into multiple runs. Each run receives an equal share of the rise and uses the selected slope ratio. The number of runs is rounded up to a whole number, and landings are placed at each end and between runs. This is a simplified layout; a real turning ramp may need a larger landing or a different configuration.

• Horizontal run = vertical rise × slope ratio denominator
• Sloped ramp length = √(rise² + horizontal run²)
• Angle from level = arctan(rise ÷ horizontal run)
• Percent grade = (rise ÷ horizontal run) × 100
• Ramp runs = ceiling(total rise ÷ maximum rise per run)
• Landing count = ramp runs + 1 (top, bottom, and intermediate landings)

Worked example: 24-inch rise at 1:12

Suppose an entrance is 24 inches above the approach and the design scenario uses a 1:12 slope. The horizontal run is 24 × 12 = 288 inches, or 24 feet. The sloped ramp surface is √(24² + 288²) = about 289 inches, or about 24.1 feet. The angle is approximately 4.76 degrees. The difference between sloped length and horizontal run is small at this slope, but both dimensions are useful for planning.

If the project uses a 30-inch maximum rise per run, this 24-inch rise fits within one run. The calculator therefore includes two landings: one at the top and one at the bottom. With a 60-inch landing depth at both ends, the simple footprint length is 24 feet plus 10 feet of landing depth, or 34 feet. A real landing may need additional width, door maneuvering clearance, or space for a turn.

Now consider a 48-inch rise using the same 1:12 ratio and 30-inch maximum rise per run. The calculator divides the rise into two runs and shows three landings. The total horizontal ramp run is 48 feet, before the landing areas are added. This illustrates why even a modest rise can require substantial space. Measure the site and verify all required dimensions before construction.

ADA ramp slope and accessibility standards

In the 2010 ADA Standards for Accessible Design, a ramp run on an accessible route generally has a maximum running slope of 1:12. A ramp run also has a maximum rise of 30 inches before a landing is required. The Standards address clear width, cross slope, landings, surfaces, handrails, edge protection, and other details. Limited exceptions apply in specific circumstances, so the 1:12 value should not be treated as the only design requirement.

The U.S. Access Board's ramp guide summarizes common ADA provisions, including a 36-inch minimum clear ramp width in many cases, a 1:48 maximum cross slope, and level landings at the top and bottom of each run. Some rules differ for curb ramps, play areas, existing facilities, employee work areas, or other special settings. State and local building codes may also add requirements.

Use the slope presets to compare geometry, not to claim compliance. The calculator does not evaluate doors, maneuvering clearances, handrail extensions, curb ramps, edge protection, protruding objects, detectable warnings, or route connection. Review the official standard and local code, and have the design checked by a qualified professional or relevant authority before building.

Landings, turns, and total ramp footprint

Landings provide level space at ramp ends and where a ramp changes direction. They affect the space needed much more than the sloped run alone. The calculator counts one landing at each end and one between runs. It multiplies the landing count by the entered landing depth and ramp width to estimate landing surface area. The total footprint length is the horizontal run plus the landing depths in a straight-line layout.

A 90-degree or 180-degree turn may fit more easily in a site than one long straight ramp, but it needs a landing sized and arranged for the turn. The calculator uses the same landing depth for each location and does not draw a full switchback plan. Top and bottom landings may also need space for door swings, thresholds, maneuvering, or connection to another walkway.

Check the complete route from arrival point to entrance, not just the ramp. Existing sidewalks, property lines, drainage, utilities, doors, steps, and landscaping can constrain the layout. A long ramp may require rails, edge protection, lighting, drainage, and regular maintenance. If a ramp cannot fit while meeting required dimensions, explore other compliant access solutions with a qualified designer.

Ramp width, handrails, and edge protection

Ramp width should be measured as clear travel width. Handrails, curbs, guards, or other elements can reduce the usable space. The calculator compares the entered width with a common 36-inch (915 mm) ADA clear-width reference and displays a reminder if the value is below it. The exact requirement can depend on the standard, use, and exceptions; verify it for your project.

Where handrails are required, they generally affect both sides of the ramp and need appropriate height, gripping surface, continuity, and extensions. This tool can estimate a simple railing length from the sloped run and an optional end extension, but it does not specify rail height, shape, clearances, returns, posts, guards, or attachment strength. Use the applicable standards and product details to design the actual rail system.

Edge protection may be needed to help prevent wheels or mobility devices from slipping off the ramp. A handrail is not automatically a substitute for every edge-protection requirement. Surface firmness, stability, slip resistance, drainage, cross slope, transitions, and threshold changes also matter. These details cannot be confirmed by a length calculator.

Choosing a ramp slope for comfort and available space

A flatter ramp has a lower grade and requires more horizontal space. A steeper ramp is shorter but can be harder to travel and may not meet accessibility requirements. The 1:12 preset is a common maximum slope reference under the ADA Standards for many ramp runs. Where the site allows, a gentler slope may improve usability, though it still needs proper landings, width, surface, and other design elements.

The actual effort to use a ramp depends on the person, mobility device, load, weather, surface, and direction of travel. A wheelchair user may need a flatter slope than a standing person carrying items. Caregivers, carts, walkers, scooters, and powered devices can have different needs. If the ramp is for regular use, talk with the intended users and a qualified accessibility professional about the whole route.

Do not select a steep slope because it fits more easily on paper. Accessibility standards allow certain steeper slopes only in defined situations with restrictions. If the available space is limited, a switchback, reconfigured entrance, lift, or other access solution may be appropriate. Confirm options with the building authority or design professional.

Materials, surface, drainage, and construction

Ramp construction may use concrete, wood, metal, or modular components. The correct structure depends on the height, span, supporting ground, loads, weather, and whether the ramp is permanent or temporary. A ramp surface should be firm, stable, and slip-resistant for its intended use. Materials and coatings should be suitable for wet conditions and local temperature changes.

Outdoor ramps need drainage so water does not pond, flow into a building, or freeze across the travel path. The running slope is in the direction of travel, while cross slope runs across the width. Accessibility rules can restrict cross slope. The calculator does not design drainage or cross slope, so include these issues in site planning and use construction details that meet local requirements.

Footings, posts, guards, handrails, fasteners, and connections must support expected loads. A dimensional estimate does not size those components. Obtain permits where required and use plans that meet applicable codes. For a permanent ramp, especially a raised or long structure, ask a qualified builder or engineer to assess the foundation and structural details.

Common ramp planning mistakes

A frequent mistake is calculating only the sloped length and forgetting horizontal run. The two are close for a shallow ramp but are not the same dimension. Another is leaving out landings, which can add several feet to the footprint and may determine whether a layout fits. Include the top, bottom, and intermediate landing areas when measuring the site.

People also confuse the slope ratio direction. A 1:12 ramp rises one unit vertically for twelve units horizontally, not the reverse. Enter rise as the vertical height difference between the lower and upper surfaces. Measure finished elevations where possible; rough ground measurements can miss thresholds, door sills, or grade changes.

A final mistake is treating a 1:12 result as proof that the ramp meets every accessibility rule. Width, cross slope, landings, rails, edge protection, surface, drainage, and route details still need review. Check the local code and standard for the building type. If the ramp is for a person with specific mobility needs, involve them in planning and seek appropriate professional advice.

Metric and imperial ramp calculations

Imperial mode accepts rise, width, landing depth, and maximum rise per run in inches. It displays run and sloped length in feet and area in square feet. Metric mode accepts those dimensions in millimetres and displays run and length in metres and area in square metres. The slope ratio stays the same when units change because it is a proportion, not a length.

One foot is 12 inches, and one inch is 25.4 millimetres. A rise of 30 inches equals 762 millimetres, while accessibility references may round this to 760 millimetres. The calculator converts your inputs exactly and displays rounded values for readability. Use the source document and local code's stated dimensions for final plans rather than relying on display rounding.

Check the unit labels before entering values. If using metric, do not enter a rise in centimetres into a millimetre field without conversion. If using imperial, decimal inches are accepted: 6.5 inches means six and one-half inches. Confirm that width, landing dimensions, and rise use the same selected mode.

Limits and next steps

This calculator models straight, constant-slope ramp runs with equal rise per segment and repeated landing dimensions. It estimates the total horizontal run, sloped surface, landing area, and simple footprint. It does not prepare drawings, check property boundaries, assess existing conditions, size structural members, or confirm code compliance. It also does not address vehicle ramps, curb-ramp flares, stairs, or specialized transport equipment.

Official accessibility standards and local building rules can change and may include exceptions or requirements not represented here. Use current regulations for your location and project. The ADA references below are U.S. federal standards; they do not automatically apply in other countries, and local requirements may be more specific.

Use the estimate to understand the space and compare slope scenarios. Before construction, verify rise, run, landings, width, cross slope, rails, edge protection, surface, drainage, and structural design with the responsible authority and qualified professionals. Make accessibility decisions with the people who will use the route.