Calculator Inputs
Formula Used
How to Use This Calculator
Example Data Table
| Rise (in) | Run (in) | Slope (%) | Ratio | Note |
|---|---|---|---|---|
| 6 | 72 | 8.33 | 1:12 | Common maximum slope example |
| 12 | 144 | 8.33 | 1:12 | Same slope at double rise |
| 24 | 240 | 10.00 | 1:10 | Too steep for typical ramps |
| 30 | 360 | 8.33 | 1:12 | Often paired with rise-per-run check |
Article
Accessible ramp layout is a recurring coordination issue in construction because geometry affects grading, doorway transitions, drainage, and structural framing. A ramp is defined by its vertical rise and horizontal run, and slope is calculated as rise divided by run. Teams often begin with a target ratio such as 1:12, then confirm the available footprint can provide the required run while still allowing landings, turning space, and safe transitions at the top and bottom. Early calculations reduce redesign cycles, improve budget certainty, and help avoid last minute field fixes.
Use this calculator in three practical ways. First, if you have field dimensions, enter rise and run to obtain slope percent, slope ratio, and ramp angle. Second, if you know the rise but want a target slope, enter the rise and a ratio of 12 to compute the minimum run needed for that rise. Third, if the site fixes the run length, enter run and ratio to estimate the achievable rise and compare it to the required elevation change. Planning inputs also help split a long ramp into multiple runs by limiting rise per run and estimating the number of landings.
Example data: a 24 in rise from sidewalk to entry needs a minimum run of 24 × 12 = 288 in (24 ft) to achieve a 1:12 slope. That equals 8.33% and an angle of about 4.76°. If only 240 in of run is available, slope becomes 10% (about 5.71°), which is typically too steep for a standard ramp run. Options include adding a switchback, regrading the approach, shifting the entry point, or selecting an alternate route with a smaller rise. Record the chosen values so later grading changes do not erase accessibility intent.
For multi run layouts, many projects limit vertical rise per run (often 30 in). A 42 in total rise with a 30 in maximum rise per run yields two runs and three landings, so the footprint must include both ramp runs plus landing lengths, turning clearances, and door maneuvering space if an entry door is nearby. Cross slope and clear width influence usability and inspection outcomes; lower cross slope improves wheel stability, and adequate width supports handrail clearance and maintenance. Coordinate edge protection, handrails, surface traction, and drainage details with finishes and waterproofing. Export the CSV or PDF to share calculations with drafting, estimating, and field supervision.
Build compliant ramps faster with clear slope insights today.
FAQs
It means one unit of rise for every twelve units of horizontal run. For example, 6 inches of rise needs 72 inches of run at a 1:12 ratio.
Enter the rise and choose “rise and slope ratio,” then set the ratio to 12. The calculator multiplies rise by the ratio to estimate minimum run.
Percent and angle help compare ramp alternatives and communicate with different trades. Inspectors and designers often discuss slope in percent, while layout and grading teams may prefer angles or ratios.
The tool divides total rise by the max rise per run you set, rounds up to whole runs, then adds one landing for each run plus the top and bottom.
A common trigger is rise greater than 6 inches or run greater than 72 inches. Always confirm handrail requirements, extensions, and clearances in the governing standard.
Cross slope is the side to side slope across the ramp surface. Keeping it low improves wheel stability, reduces drift, and helps users maintain direction, especially in wet conditions.
Use it as an early design and documentation aid. Final compliance depends on the complete ramp system, landings, clearances, surface details, and local interpretations by the authority having jurisdiction.