Skip to content
🛠️
Whiz Tools

ADA Ramp Calculator: Length, Slope & Angle

Calculate the required length, slope, and angle for a wheelchair ramp from its rise. Checks results against ADA 1:12 slope and landing rules, free and instant.

Ramp Calculator for Accessibility

This calculator helps you determine the proper measurements for an accessible ramp based on ADA standards. Enter the desired rise (height) of your ramp, and the calculator will determine the required run (length) and slope.

Input Measurements

inches

Calculated Results

Required Run (Length)
72.0inches
Slope
8.33%
Angle
4.76°
✓ This ramp meets ADA accessibility standards

Ramp Visualization

Ramp Visualization: Rise 6 inches, Run 72.0 inches, Slope 8.33%Rise: 6"Run: 72.0"Slope: 8.33%

ADA Standards

According to ADA standards, the maximum slope for an accessible ramp is 1:12 (8.33% or 4.8°). This means for every inch of rise, you need 12 inches of run.

Loading calculator...
📚

Documentation

Ramp Calculator for ADA Accessibility

A ramp calculator works out how long a wheelchair ramp must be, how steep it will be, and what angle it makes with the ground, based on the height it needs to climb. It checks the result against the slope and landing rules in the Americans with Disabilities Act (ADA).

Key terms

  • Rise: the vertical height the ramp must climb, measured from the ground to the top landing or doorway.
  • Run: the horizontal distance the ramp covers.
  • Slope: how steep the ramp is, given as a ratio (1:12) or a percentage (8.33%).
  • Angle: the same steepness expressed in degrees.
  • Landing: a flat, level platform at the top, bottom, or partway along a ramp.

How to calculate ramp length (run)

The 2010 ADA Standards for Accessible Design, section 405.2, cap the running slope of a ramp at 1:12. That means 1 inch of rise for every 12 inches of run.

Run = Rise × 12

A ramp with a 10-inch rise needs a run of 120 inches, or 10 feet.

How to calculate ramp slope

Slope (%) = (Rise ÷ Run) × 100

At the maximum ADA ratio of 1:12, the slope works out to about 8.33%.

How to calculate ramp angle

Angle (°) = arctan(Rise ÷ Run) × (180 ÷ π)

A ramp built at the maximum 1:12 slope has an angle of about 4.76 degrees.

ADA rules for ramp runs and landings

Section 405 of the ADA standards sets several rules that apply together, not just the slope:

  • Maximum slope: 1:12, about 8.33% or 4.76°.
  • Maximum rise per run: 30 inches. A single continuous ramp section cannot climb more than 30 inches before it needs a level landing.
  • Landing length: at least 60 inches, measured in the direction of travel.
  • Minimum clear width: 36 inches.
  • Handrails: required on both sides of any run with a rise over 6 inches.

If the total rise is more than 30 inches, the ramp must be split into shorter runs. Each run can rise no more than 30 inches, with a level landing between runs. The number of runs needed equals the total rise divided by 30, rounded up. The number of landings between runs is one fewer than the number of runs.

Example calculation

A porch with three 8-inch steps has a total rise of 24 inches.

  • Run: 24 × 12 = 288 inches (24 feet)
  • Slope: (24 ÷ 288) × 100 = 8.33%
  • Angle: arctan(24 ÷ 288) × (180 ÷ π) ≈ 4.76°
  • The rise, 24 inches, is under the 30-inch limit, so the ramp fits in one run and meets ADA standards.

Example with landings

A loading dock has a 72-inch (6-foot) rise.

  • Run: 72 × 12 = 864 inches (72 feet)
  • Number of runs: 72 ÷ 30 = 2.4, rounded up to 3
  • Intermediate landings: 3 − 1 = 2
  • Total horizontal length: 864 + (2 × 60) = 984 inches (82 feet), not counting the separate landings required at the very top and bottom of the ramp

Because no single run can rise more than 30 inches, this ramp needs two intermediate landings in addition to the ones at the top and bottom.

Why the slope limit is 1:12

A shallower slope takes less strength and balance to climb in a manual wheelchair. Steeper ratios such as 1:8 or 1:10 use less space but are harder to control, especially going downhill. New construction generally must meet the 1:12 maximum; some codes allow steeper slopes in limited renovation cases, but 1:12 is the standard target.

When a ramp will not fit

A ramp needing 70 or 80 feet of straight run rarely fits on a small lot. Builders often bend the run into an L-shape or a switchback, with a landing at each turn, or replace the ramp with a platform lift or an elevator where the site is too tight for any ramp layout.

Frequently asked questions

How do I calculate the length of a wheelchair ramp? Multiply the rise by 12. A 20-inch rise needs a 240-inch (20-foot) run.

What is the maximum ADA slope for a ramp? 1:12, which is about 8.33%, or an angle of roughly 4.76°.

How many steps can I have before a ramp needs landings? It depends on total rise, not the number of steps. Once total rise passes 30 inches, the ramp needs at least one intermediate landing. Three 8-inch steps (24 inches) fit in a single run; four 8-inch steps (32 inches) do not.

Do residential ramps have to meet ADA standards? Private homes are generally not required to follow the ADA, which applies to public and commercial buildings. Many homeowners still use the 1:12 ratio because it is the slope tested to be usable safely.

When does a ramp need handrails? Any run with a rise over 6 inches needs handrails on both sides, under ADA section 405.8.

How wide does an accessible ramp need to be? At least 36 inches of clear width between handrails, under ADA section 405.5.

References

  1. U.S. Department of Justice, "2010 ADA Standards for Accessible Design," section 405 (Ramps). ada.gov
  2. U.S. Access Board, "Ramps and Curb Ramps." access-board.gov