Ramp slope calculator
Turn a vertical rise and target rise-to-run ratio into the horizontal run, surface length, angle, grade, and a practical run-and-landing plan.
Ramp specifications
Ramp details
Run and landing plan
| Segment | Rise | Horizontal run | Surface length | Direction |
|---|---|---|---|---|
| Run 1 | 17.50 in | 23 ft 4 in | 23 ft 5 in | Forward |
| Run 2 | 17.50 in | 23 ft 4 in | 23 ft 5 in | 90° turn |
The planner divides rises above 30 inches into equal runs, reflecting the common 30-inch maximum rise per ramp run in accessibility guidance. Confirm landings, width, handrails, edge protection, drainage, and local code requirements separately.
How to use this ramp slope calculator
What this calculator does. This tool estimates the geometry of an inclined ramp from a vertical rise and a rise-to-run ratio. It returns the required horizontal run, the sloped surface length, the angle in degrees, the grade percentage, and a simple multi-run plan when the rise exceeds 30 inches. It is useful for early layout and material estimating, but it does not certify a design, account for structural loading, choose a slip-resistant surface, or replace review by the authority having jurisdiction.
When to use it. Use it to estimate a wheelchair-access ramp before drawing a site plan, compare a 1:12 maximum slope with a gentler 1:16 or 1:20 option, check how much horizontal space is needed to overcome steps or a porch height, or divide a long ramp into practical runs and landings. The U.S. Access Board ramp guide explains the federal accessibility provisions that commonly inform these early calculations.
How to calculate. The calculator opens with a ready-to-use demonstration: a 35-inch rise, a comfortable 1:16 slope, and one 90-degree turn. A validated example workbook is immediately available.
- Choose an Application preset or select Custom ratio.
- Review or replace the Rise-to-run ratio (1 : n). A larger denominator makes the ramp gentler and longer.
- Select the Ramp type to describe whether the layout is straight, turns once, or switches back.
- Enter the vertical Rise and choose inches, feet, centimeters, or meters. Results update live.
- Read the required run and secondary geometry, review the segment table, then choose Download Excel to export the current calculation. Reset clears the demonstration values, results, and workbook state; Excel export remains unavailable until a complete valid rise and ratio are entered again.
Input guide. Application is a required preset selector. “ADA maximum – 1:12” uses a 12-unit run per unit rise; “Comfortable – 1:16” and “Gentle walkway – 1:20” create progressively longer, shallower ramps. The existing-site presets are included for comparison only and should not be treated as automatic permission. Rise-to-run ratio (1 : n) is a required positive decimal from 1 to 1000; for example, 16 means 1:16. Do not enter “1:16” in the field – enter only 16. Ramp type is required for the planning labels but does not alter the total geometric length. Rise is required, must be greater than zero, and accepts ordinary en-US decimal notation without scientific notation. A value such as 35 inches is realistic; negative values, decimal commas such as 1,5, and pasted unit text are rejected. Changing the unit converts the current rise so the physical height stays the same.
Output guide. Required horizontal run is the level-plan distance and is the main space-planning result. Ramp surface length is the hypotenuse, useful for an initial decking or surface-length estimate. Slope angle is the inclination above horizontal. Elevation grade is rise divided by run times 100; 100% means 45 degrees, not 90 degrees. Planned ramp runs divides the rise into equal runs so no run exceeds 30 inches of rise; Intermediate landings is one fewer than the number of runs; and Longest run is the maximum horizontal segment in the plan. The summary pills repeat the ratio, grade, run count, and a simple comparison with the 1:12 slope threshold. Each row in the table reports one segment's rise, horizontal run, sloped length, and direction label. These are geometric estimates, not a code approval.
Worked example. For the startup values, rise is 35 inches and the ratio is 1:16. Horizontal run equals 35 × 16 = 560 inches, or 46 feet 8 inches. Surface length equals √(560² + 35²) = 561.09 inches, which displays as about 46 feet 10 inches. The angle is arctan(35 ÷ 560) = 3.58°, and grade is 35 ÷ 560 × 100 = 6.25%. Since 35 inches exceeds the 30-inch rise-per-run planning threshold, the model creates two equal runs of 17.5 inches rise each, with one intermediate landing.
Learn more. The current federal technical requirement for ramp runs is commonly expressed as a slope not steeper than 1:12; review the Access Board's Chapter 4 accessible-route provisions and the 2010 ADA Standards for Accessible Design. For workplace contexts, OSHA's definition of a ramp as an inclined walking-working surface provides useful terminology, but workplace requirements can differ from public-accessibility rules.
How the ramp formulas work
Run = Rise × ratio denominator
Grade (%) = Rise ÷ Run × 100
Angle = arctan(Rise ÷ Run)
Surface length = √(Rise² + Run²)
All dimensions are converted to inches internally, so changing the display unit does not change the physical result. The calculator retains unrounded values for the workbook and rounds only the displayed text. A larger ratio denominator increases both horizontal run and surface length while decreasing angle and grade. For example, changing 1:12 to 1:20 keeps the rise fixed but increases required run by two-thirds.
Planning cautions
Slope is only one part of a safe ramp. Real projects may need compliant clear width, level landings, handrails, edge protection, turning space, drainage, frost protection, guards, structural design, and a slip-resistant surface. Existing buildings can have exceptions that depend on site constraints, dates, jurisdiction, and the exact work being performed. Treat the calculator as an early geometry and estimating aid, then verify the complete design against current local requirements and project-specific conditions.