Ramp Length Calculator

A ramp length calculator returns the horizontal run and surface length a ramp needs for a set rise. It multiplies the rise by the slope ratio, such as 12 for the ADA's 1:12 maximum, and converts to feet to get the run. It then takes the hypotenuse of that run and the rise to get the surface length.

Last reviewed September 2026Method & sources Report an error

Not to scale.

Ramp Length (surface)

12.04 ft

Breakdown
Ramp Length (surface)	12.04 ft
Required Horizontal Run	12.00 ft

How to Calculate Ramp Length

At a given maximum slope ratio (like the ADA's 1:12), the required horizontal run is the rise multiplied by that ratio (`rise × 12` for a 1:12 slope, converted to feet). A gentler ratio (1:16 or 1:20) needs proportionally more run for the same rise. The ramp's actual surface length is then the hypotenuse of that run and the rise (`√(run² + rise²)`). It is slightly longer than the horizontal run alone, since the ramp surface itself travels at an angle rather than perfectly horizontally.

Example: 12 in. rise, using the ADA's 1

A 12 in. rise, using the ADA's 1:12 maximum slope: 1. Required run: 12 × 12 ÷ 12 = 12 ft 2. Rise in feet: 12 ÷ 12 = 1 ft 3. Ramp length: √(12² + 1²) = √145 ≈ 12.04 ft That rise needs at least 12 ft of horizontal run, with an actual ramp surface length of about 12.04 ft.

What Is Ramp Length?

A ramp length calculator finds the minimum horizontal run and actual surface length needed for a ramp to overcome a given rise without exceeding a maximum slope. It complements the Elevation Grade calculator, which checks whether an existing rise/run combination already meets the ADA's slope maximum. This calculator instead solves for the run a new ramp needs from the rise alone.

Ramp Length: Pros and Cons

Pros

Solves directly for the run and length a new ramp needs, rather than only checking an existing rise/run pair (see Elevation Grade for that check)
Covers the ADA maximum (1:12) plus two gentler, easier-to-navigate ratios (1:16, 1:20)
Reports both the horizontal run (what you'd measure and stake out) and the actual ramp surface length (what determines the ramp material needed)

Cons

Gives the minimum run for slope compliance only. A full ADA-compliant ramp design also has separate requirements for level landings (at the top, bottom, and at intervals along a long ramp), handrails, edge protection, and cross-slope, none of which this calculator checks
The ADA's 1:12 maximum sometimes has a shorter maximum run before a landing is required (commonly 30 ft of horizontal run at maximum slope before a landing). A rise requiring a longer ramp than that needs to be broken into multiple ramp runs with landings between them
A residential ramp (not open to the public) isn't always legally required to meet full ADA standards, though following them is still good accessibility practice. Check what applies to your specific situation

Ramp Length: What a Pro Checks

Check whether your rise needs a landing partway up. ADA standards require a landing at least every 30 ft of horizontal run at the 1:12 maximum slope, so a long rise may need to be split into multiple ramp segments with landings between them.
Consider a gentler slope than the 1:12 ADA maximum if you have the space. 1:16 or 1:20 is easier to navigate, especially for someone with limited strength or an unpowered wheelchair, though it needs proportionally more horizontal run.

Frequently Asked Questions

How much ramp length do I need for a given rise?

At the ADA's 1:12 maximum slope, multiply the rise by 12 for the required horizontal run (in the same units). Then find the actual ramp surface length as the hypotenuse of that run and the rise. A 12 in. rise needs at least 12 ft of run and about 12.04 ft of actual ramp length.

What is the ADA's maximum ramp slope?

1:12, meaning at least 12 in. of horizontal run for every 1 in. of vertical rise (about 8.33%), per the ADA Standards for Accessible Design, Section 405.2.

Is a gentler ramp slope than 1:12 better?

Yes, where space allows. A gentler slope (1:16 or 1:20) is easier to navigate, especially for someone with limited strength or an unpowered wheelchair, though it needs proportionally more horizontal space for the same rise.

Does a ramp need a landing?

Yes, per ADA standards. Level landings are required at the top and bottom of every ramp run, and at intervals along a long ramp (commonly at least every 30 ft of horizontal run at the maximum 1:12 slope). This calculator finds the run/length for a single ramp segment, not a multi-segment ramp with landings.

Does a home ramp have to follow ADA standards?

Not always legally, for a private residence not open to the public. Following ADA slope and landing guidelines is still widely considered good accessibility practice for a home ramp, and may be required if the home falls under certain assistance program or code requirements.

Sources

U.S. Access Board, ADA Standards for Accessible Design, Section 405.2: ramp running slope maximum (1:12) (opens in a new tab)

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