A ramp is an inclined pathway that is built with a slope exceeding 1:20, meaning that for every 20 inches of horizontal length, or run, there is a vertical rise of one inch. It is mandatory for ramps to adhere to the established ADA guidelines for ramps.

What is the method for calculating the slope of a ramp?

The slope can be expressed as percentage, angle or rise: run ratio.

  1. Rise / Run ratio
  2. This is the ratio of one part rise to the corresponding part of the run. It can be expressed as 1:12 or 1/12 or 1 in 12. Typical slope are 1:12, 1:20 and 1:8. e.g. 1:12 means for every 1 feet of vertical rise, 12 feet horizontal length are required.

    Slope (Ratio) = Rise: Run
  3. Angle
  4. It's the degree to which the ramp is tilted with respect to the run, or the angle at which the ramp rises above the horizontal.

    Slope (Angle) = tan-1 (
    Rise (h)/Run (d)
  5. Slope (%)
  6. The slope can be expressed in percentage, which is calculated by dividing the height that has to be climbed (h) by the horizontal distance (d) and multiplying the result by 100.

    Slope (%) =
    Rise (h)/Run (d)
    x 100
    What is a 100% slope?

    A slope of 45 degrees above the horizontal is equal to 100%. It has the same width (run) and height (rise) as well. For slope to be 100%, Rise should be equal to Run.
    When rise= run,
    Angle = tan-1(1) = 45°

ADA guidelines for ramp

The Americans with Disabilities Act's (ADA) 2010 Standards provide baseline criteria for newly constructed public buildings. In addition to a wide range of accessibility norms, it also includes ramp building guidelines. In this section, we'll explore ADA ramp slopes in further detail.

  1. General
    • Ramps should ideally be placed outside. Inside ramps are not advisable since they take up a lot of room.
    • The ramp's entrance should ideally be situated next to the steps.
  2. Slope
    • A ramp's slope must not exceed 1:12 in new buildings.
    • 1:16 is the comfortable slope.
    • The minimal slope is 1:20; anything less is not considered a ramp, therefore there is no need for railings.

    Maximum rise allowed in each case is 30 inches (760 mm).

    In cases where there are space limitations in existing sites, buildings, and facilities, steeper ADA ramp slopes may be allowed. However, there are stricter restrictions on the maximum rise that apply.

    SlopeMaximum Rise
    1:8 to < 1:103 inches (75mm)
    1:10 to < 1:126 inches (150mm)

    Please keep in mind that according to the ADA, slopes that are steeper than 1:8 are prohibited.

  3. Clear width
  4. The minimum required width for a ramp to be considered accessible is 36 inches (915 mm). It is important to consider the mounting of handrails during the design of a ramp.

  5. Landings
  6. It is important for every ramp to have level landings at both the top and bottom of each section, particularly if the ramp has multiple sections or turns. The essential landing features are as follows:

    • The minimum required landing length is 60 inches (1525mm), and it is recommended that the landing's width be equal to or greater than the ramp's run.
    • In order to ensure safe maneuvers, it is important to provide sufficient space. For instance, if the ramp construction changes direction by making a 90-degree turn, the minimum landing size required is 60 inches by 60 inches.

  7. Handrails
  8. If the rise is greater than 6 inches and the run is greater than 72 inches, then handrails are required on both sides in order to meet the ADA standards.

  9. Miscellaneous
  10. The ramps must adhere to certain guidelines for safety purposes.

    • The cross slope or camber should not exceed 1:50.
    • The ramp should be constructed using suitable materials to prevent any sliding or slipping.
    • It is also important to have edge protection and handrail extensions.
    • If the ramp is outdoors, it is crucial to consider weather conditions and ensure proper drainage.