Ramp Calculator
ConstructionCalculate the required run length and total ramp length for a wheelchair or accessibility ramp. Supports ADA 1:12 slope and other common slope ratios.
Required Run Length
30
Total Ramp Length
30.1
What is a Ramp?
A Ramp Calculator determines the horizontal run length and total sloped ramp length needed to safely rise a given height, based on a chosen slope ratio such as the ADA-standard 1:12. This calculation is essential for designing accessible ramps, loading ramps, or any sloped access path where the relationship between rise, run, and slope needs to be precise.
For accessibility ramps specifically, meeting the correct slope ratio isn't just a design preference — it's often a legal requirement under ADA guidelines for public and commercial spaces. If you're building the ramp surface itself, pair this with the Decking Calculator for board material, or the Concrete Weight Calculator if pouring a concrete ramp.
How to use this Ramp calculator
- Enter the Rise Height in inches — the total vertical distance the ramp needs to climb.
- Select your Slope Ratio — 1:12 (ADA) is the standard for accessible ramps; steeper ratios are available for non-code applications.
- Review the Required Run Length result to check if it fits your available space.
- Review the Total Ramp Length result for material planning along the sloped surface.
- If the run length doesn't fit your space, consider a switchback ramp design or confirm whether a steeper (non-ADA) ratio is acceptable for your application.
Formula & Methodology
The calculator uses the slope ratio to find run length, then the Pythagorean theorem for total ramp length: Run Length = Rise Height × Slope Ratio Denominator Total Ramp Length = √(Rise Height² + Run Length²) Worked example: For a 30 in rise using the ADA 1:12 slope ratio: Run Length = 30 × 12 = 360 in = 30 ft Total Ramp Length = √(30² + 360²) = √(900 + 129,600) = √130,500 ≈ 361.25 in ≈ 30.1 ft This confirms that a 30-inch rise at the ADA-standard slope requires roughly 30 feet of horizontal space, with the ramp surface itself only marginally longer than the run due to the gentle slope.
Frequently Asked Questions
The ADA (Americans with Disabilities Act) requires a maximum slope ratio of 1:12 for wheelchair-accessible ramps, meaning 1 inch of rise for every 12 inches of horizontal run. This is the gentlest and safest standard slope ratio, and it's the default option in this calculator.
Ramp length is calculated as the hypotenuse of a right triangle formed by the rise height and the required horizontal run, using the Pythagorean theorem. This calculator computes both the run length and the total sloped ramp length automatically from your rise height and chosen slope ratio.
Steeper ratios like 1:8 or 1:10 use less horizontal space but are not ADA-compliant for public accessibility ramps and are harder for wheelchair users to navigate independently. Steeper ratios are sometimes used for temporary or non-code-regulated ramps where space is limited, but 1:12 remains the standard for accessible design.
ADA guidelines generally require a level landing platform for every 30 inches of rise on a 1:12 slope ramp, meaning long ramps need to be broken into segments with flat rest areas between them. Check current ADA guidelines for exact landing requirements based on your total rise.
At the standard 1:12 ADA slope, a ramp needs 12 inches of horizontal run for every 1 inch of rise — so a 30-inch rise (a typical single step plus porch height) requires 30 feet of horizontal run at minimum, which is often the limiting factor in ramp design for tight spaces.
Run length is the horizontal distance the ramp covers, while total ramp length is the actual sloped surface distance a wheelchair travels along, which is always slightly longer than the run due to the rise component — this calculator provides both figures.
Yes, the same rise-run-length geometry applies to any ramp, including loading ramps, wheeled equipment ramps, or temporary access ramps — simply select a slope ratio appropriate for your application, even if it's steeper than the ADA standard.
This calculator focuses on rise, run, and slope-based length — ramp width is a separate design consideration (ADA specifies a minimum clear width, commonly 36 inches) that doesn't affect the run length or ramp length calculations shown here.
The Total Ramp Length figure tells you the sloped surface length to plan for decking, railing, or concrete pour along the ramp's actual travel path — pair it with the [Decking Calculator](/decking-calculator/) if building a wood ramp surface.
Also known as