Ramp Calculator uses rise and planned run to calculate slope ratio, required run, surface length, pitch angle and grade. Formula: slope ratio = run ÷ rise, with ADA 1:12 slope status shown.
The Ramp Calculator uses total vertical rise and planned horizontal run to calculate actual slope ratio, required horizontal run, ramp surface length, pitch angle, and grade percentage. Select ADA Public / Commercial mode to check your slope against the 1:12 target used in accessible route design standards.
Enter your rise and run, choose a measurement system and a target application, then read each result card for slope ratio, required run, surface length, and pass/fail status for the selected slope target.
What the Calculator Measures
Compares horizontal run to vertical rise, expressed as 1:N. A 1:12 ratio means 12 inches of horizontal travel for every 1 inch of rise. The larger the second number, the shallower and more accessible the ramp.
The exact horizontal distance needed to reach the selected target ratio for the measured rise. If the planned run is shorter than this value, the ramp is steeper than the target and the slope will not pass.
The inclined material length of the ramp — the hypotenuse of rise and planned run. This is the physical length of decking, steel plate, or concrete formwork that needs to be ordered or installed. It is based on the user's planned run, not the required run.
The angular incline of the ramp from level ground, expressed in degrees. A 1:12 slope equals approximately 4.76°. A lower pitch angle means a more gradual ramp surface.
Rise divided by run, expressed as a percentage. An 8.33% grade corresponds to a 1:12 slope. Grade is the standard slope format used in civil engineering plans, site drawings, and paving specifications.
Pass or Fail checked against the selected target application only. A Slope Pass confirms the planned run meets or exceeds the selected target ratio. This result does not verify compliance with all applicable code requirements.
In ADA Public / Commercial mode, the calculator flags handrail requirements when rise exceeds 6 inches (150 mm), consistent with ADA ramp standards. For Residential, Utility, and Equipment modes, the handrail result shows Check Code — verify handrail requirements against the applicable building code and the authority having jurisdiction for the project location.
How the Calculator Computes Each Result
Divides the planned run by rise to find how many horizontal units correspond to each vertical unit. The result is displayed as 1:N, where N is the run-per-rise value. A higher N means a shallower ramp.
Multiplies rise by the target ratio number to find the minimum horizontal run needed to meet the selected standard. The planned run must equal or exceed this value to achieve a Slope Pass.
Applies the Pythagorean theorem to rise and planned run to calculate the hypotenuse. This is the actual physical length of the inclined ramp surface — the material length, not the horizontal ground footprint.
Applies the arctangent of rise over run to find the incline angle from level ground in degrees. A smaller angle means a more gradual ramp. A 1:12 slope produces approximately 4.76°.
Divides rise by run and multiplies by 100 to express slope as a percentage. A 1:12 slope equals 8.33% grade — the same slope in a different unit. Grade percentage is the standard format for civil engineering documents, curb ramp specifications, and site-grading plans.
Worked Example: 24 in Rise, 288 in Run
Target Application Options
Checks the planned ramp slope against the 1:12 maximum slope target referenced in ADA accessibility standards for accessible routes. A rise greater than 6 inches (150 mm) triggers a handrail flag. Slope alone does not determine full ADA compliance — landings, width, surface quality, and edge protection also apply.
A steeper slope target for residential or private-use ramps where public accessibility requirements may not apply directly. Verify the allowable slope limit with the local residential building code before construction. The handrail result shows Check Code for this mode.
A utility-grade slope target for shed ramps, deck transitions, and equipment access paths not intended as walking or wheelchair ramps. This is not an accessibility compliance check. Verify local code requirements for the specific application.
A loading-style slope target for equipment ramps and motorcycle loading ramps. Not applicable to pedestrian, accessibility, or wheelchair ramp design. Always verify equipment manufacturer specifications and local code requirements for loading ramp applications.
Accuracy and Limitations
- The calculator assumes a straight-line rise and run. It does not account for curved ramps, switchbacks, intermediate landings mid-run, or variable-grade surfaces.
- The Planned Surface Length is the hypotenuse calculated from the user's planned run — not the required run — and represents the inclined material length for that specific input combination.
- The Selected Ratio Status checks only whether the planned ramp slope meets or exceeds the selected target ratio. It does not verify compliance with all requirements of any accessibility standard, building code, or local ordinance.
- Full ADA compliance is not determined by slope alone. Compliant accessible ramp design also requires proper landing dimensions, minimum clear ramp width, surface material and texture, edge protection, and handrail specifications — all governed by the applicable standard and local authority having jurisdiction.
- Verify the final ramp design against the applicable building code, accessibility standards, and the requirements of the authority having jurisdiction. Consult a qualified design or construction professional when required by the project.
References
- U.S. Access Board. ADA Accessibility Standards, Chapter 4: Accessible Routes. Section 405 covers ramp requirements including maximum slope (1:12), cross slope, rise limits, landing dimensions, handrail specifications, and edge protection. access-board.gov/ada
- U.S. Access Board. Guide to the ADA Accessibility Standards: Ramps and Curb Ramps. Practical guidance on applying ADA ramp requirements, including slope targets, landing configurations, clear width, and handrail provisions. access-board.gov/ada/guides/chapter4-ramps
- Local building code or authority having jurisdiction (AHJ). Project-specific ramp design requirements — including residential, commercial, and utility ramp applications — must be verified against the applicable local or regional building code and confirmed with the AHJ for the project location.