Ramp Calculator
Calculate ramp length, slope ratio, grade percent, angle, rise, and run for accessibility, shed, trailer, loading, and sitework planning.
This is a geometry calculator, not a compliance approval tool. If you are laying out steps instead of a ramp, use the Stair Calculator.
Results
Planning estimate only. This calculator does not approve ADA compliance, structural design, landing layout, handrails, edge protection, surface traction, or local code requirements.
How to use this calculator
- 01Choose Imperial or Metric units.
- 02Choose what you want to solve: ramp length, slope, rise, run from angle, or slope from ramp length.
- 03Enter the known rise, run, ramp length, slope ratio, or angle for that mode.
- 04Use the slope target presets for common 1:12, 1:16, 1:20, or 1:8 planning ratios when applicable.
- 05Review ramp length, horizontal run, rise, grade percent, angle, and the 1:12 reference note.
- 06Use the result as a geometry estimate, then confirm landings, width, handrails, surface, drainage, and local requirements before building.
Understanding the math
Ramp geometry works like a right triangle. Rise is the vertical height, run is the horizontal distance, and ramp length is the sloped side.
slope_ratio = run / rise grade_percent = rise / run x 100 angle = atan(rise / run)
run = rise x slope_ratio ramp_length = sqrt(rise^2 + run^2) rise = run / slope_ratio
run_from_angle = rise / tan(angle) run_from_length = sqrt(ramp_length^2 - rise^2)
A 1:12 reference means 12 units of horizontal run for each 1 unit of rise. Wider project requirements can still apply even when the slope geometry looks reasonable.
Ramp slope reference
Common ramp slope references for planning. Use the active unit system for examples, and confirm the final design against the rules that apply to your project.
| Reference | Typical Value | Note |
|---|---|---|
| 1:12 reference | 1 in rise / 12 in run | Common ADA maximum running slope reference for many accessibility ramps. |
| 1:16 easier ramp | 1 in / 16 in | Longer and gentler than 1:12 when space allows. |
| 1:20 walkway | 5% grade | Often treated as a sloped walk rather than a ramp in accessibility guidance. |
| 1:8 utility ramp | 12.5% grade | Steep planning reference for short utility or loading use; check the actual use case. |
| 2 ft rise at 1:12 | 24 ft run | Ramp length is slightly longer than run because of the slope. |
| Planning checks | More than slope | Width, landings, handrails, edge protection, surface, and local rules can all matter. |
Frequently asked questions
How do you calculate the slope of a ramp?
Divide the rise by the horizontal run. The calculator also shows the same slope as a 1:X ratio, a grade percent, and an angle in degrees.
How do you calculate ramp length?
Treat the ramp as the sloped side of a right triangle. After finding the horizontal run from rise and slope ratio, use length = sqrt(rise^2 + run^2).
How long does a ramp need to be for a 2 foot rise?
At a 1:12 planning slope, a 2 foot rise needs 24 feet of horizontal run, and the sloped ramp length is just over 24 feet. Gentler slopes such as 1:16 or 1:20 need more run.
What is the ADA ramp slope?
A 1:12 running slope is a common ADA maximum reference for many accessibility ramps. Full ADA or local compliance can also depend on width, landings, handrails, edge protection, cross slope, surface, and the specific site.
Is 5% slope considered a ramp?
A 5% grade is the same as a 1:20 slope. In ADA accessibility guidance, accessible route portions steeper than 5% are treated as ramps, but final classification depends on the project and local rules.
How do you calculate a wheelchair ramp?
Measure the vertical rise, choose a target slope ratio such as 1:12 or a gentler value, multiply rise by that ratio to get run, then check the ramp length, landing layout, handrails, surface, and local requirements.
Can this calculator confirm ADA compliance?
No. It checks ramp geometry against a 1:12 planning reference, but it does not approve accessibility compliance. Confirm the final design with the current ADA standards, local code, plans, or a qualified professional.
Can I use this calculator with metric measurements?
Yes. Use the Imperial/Metric toggle. Inputs, results, reference values, and examples follow the active unit system where applicable.