Softonic

Ramp Calculator

Step 1 / 4 Ramp calculator
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Plan a wheelchair ramp, deck ramp or access ramp from the vertical rise and a target run ratio such as 1:12. The calculator estimates horizontal run, sloped surface length, slope percent, angle, run count, intermediate landings, top and bottom landing pads, and surface area with waste. Use it as an early planning estimate before checking local building rules, site constraints, handrails, edge protection and drainage.

How to estimate a ramp layout

  1. 1

    Measure the rise

    Enter the vertical height from the lower finished surface to the upper finished surface, in inches.

  2. 2

    Choose the slope ratio

    Use run per 1 inch of rise. A 1:12 ramp needs 12 inches of horizontal run for every 1 inch of rise.

  3. 3

    Set width and a landing-area assumption

    Enter clear width, an assumed rectangular landing length and maximum rise per run. The estimate counts one such pad at every run endpoint; it does not design a landing layout.

  4. 4

    Add waste for materials

    Review ramp surface area, landing area and total square footage with a waste allowance for cuts, fasteners, trim and layout changes.

Ramp slope formulas and ADA planning notes

Core formulas

Ramp planning starts with a right triangle. The vertical rise is one side, the horizontal run is the other side, and the walking surface is the hypotenuse.

  • Horizontal run (in) = vertical rise × run per rise
  • Ramp surface length (in) = sqrt(horizontal run² + vertical rise²)
  • Slope percent = 100 ÷ run per rise
  • Angle = atan(1 ÷ run per rise), converted to degrees
  • Run count = ceiling(vertical rise ÷ maximum rise per run)
  • Intermediate landings = run count − 1, never below 0
  • Landing pads = run count + 1 when a ramp exists, counting top and bottom landings
  • Ramp area (sq ft) = ramp surface length in feet × ramp width in feet
  • Landing area (sq ft) = landing pads × landing length in feet × ramp width in feet

Worked example

Suppose the rise from grade to a deck is 24 in and you want a 1:12 running slope with a 36 in clear width, 60 in landings, 30 in maximum rise per run and 10% material waste.

  • Horizontal run = 24 × 12 = 288 in = 24 ft
  • Ramp surface length = sqrt(288² + 24²) = 289.0 in = 24.08 ft
  • Slope = 100 ÷ 12 = 8.33%; angle = atan(1 ÷ 12) = 4.76 deg
  • Runs = ceiling(24 ÷ 30) = 1, so there are 0 intermediate landings and 2 landing pads
  • Ramp area = 24.08 × 3 = 72.25 sq ft
  • Landing area = 2 × 5 × 3 = 30 sq ft
  • Total with 10% waste = (72.25 + 30) × 1.10 = 112.48 sq ft

Common planning targets

The U.S. Access Board ADA guide describes several important ramp requirements. Treat these as planning flags, then verify the complete code path for your project.

Item Common ADA planning value What the calculator checks
Running slope 1:12 maximum, or 8.33% Flags whether the entered ratio is at least 12
Cross slope 1:48 maximum Not calculated; field grading detail
Clear width 36 in minimum Flags any width shortfall below 36 in
Rise per run 30 in maximum Splits the rise into multiple runs when needed
Landings Required at run endpoints; dimensions depend on configuration Counts assumed rectangular pads for an area estimate only

Pitfalls and code checks

  • Using slope percent as degrees. A 1:12 ramp is 8.33%, but only about 4.76 degrees.
  • Forgetting landings. The sloped run is not the full footprint. Top, bottom and switchback landings can add a lot of area.
  • Ignoring clear width after handrails. Clear width is measured between obstructions, so posts, rails and curbs can reduce usable space.
  • Treating material area as framing design. Square footage helps with decking or surface material, but beams, posts, footings, guards, handrails and edge protection need separate design.
  • Using this as code approval. This calculator is a planning estimate, not an inspection, permit or accessibility certification. Check the ADA standards, local amendments, site slope, drainage, door clearances and professional requirements before building.

Frequently Asked Questions

A 1:12 ramp has 12 inches of horizontal run for every 1 inch of vertical rise. That is an 8.33% slope and about a 4.76 degree angle.

At a 1:12 ratio, the horizontal run is 24 ft. The sloped surface is slightly longer, about 24.08 ft, before adding landings.

The run count uses the maximum rise per run. With the common 30 in setting, a 48 in total rise becomes two ramp runs with one intermediate landing between them.

No. It compares slope and clear width with common federal planning values and estimates runs and rectangular landing pads. It does not verify landing geometry, cross slope, surfaces, handrails, edge protection, doors, clearances or local requirements.

Yes. This is a Livewire calculator, so values are sent to our server as you edit them; step-by-step mode can also include them in the URL. Do not enter sensitive information.

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