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Wheelchair Ramp Slope Calculator (ADA Compliance)

Check a ramp's slope, ratio, and incline angle against ADA accessibility guidelines from its rise and run, and see the minimum run needed to comply.

Slope
8.33% (1 : 12)
Incline angle
4.76°
Compliance
ADA maximum range -- steeper than 1:16 but within the 1:12 limit
Minimum run for ADA max (1:12)
288 cm
Run for comfortable 1:16
384 cm
Run for easiest 1:20
480 cm

Where this falls

8.3 falls in the "ADA maximum (1:12)" range.

How it works

The ADA Standards for Accessible Design cap a new ramp's running slope at 1:12 — 1 unit of vertical rise for every 12 units of horizontal run, about 8.33% or a 4.8° incline — with gentler slopes of 1:16 or 1:20 commonly recommended when there's enough space, since they're noticeably easier for someone self-propelling a manual wheelchair — verified via web search against the ADA's own published slope requirements and accessibility-industry references rather than relied on from memory. Slope percent is simply rise ÷ run × 100, the ratio is run ÷ rise (the 'X' in '1 : X'), and the incline angle is the arctangent of rise ÷ run.

Because slope is a pure ratio, it — and every figure derived from it — comes out identical whichever unit system rise and run are both measured in together, the same unit-invariant-ratio reasoning this site's Bicycle Gain Ratio and Knitting Gauge calculators already established; no internal metric/imperial conversion is needed.

The minimum run needed at each of the three standard ratios (1:12, 1:16, 1:20) is also reported directly from your entered rise — for example, a 24-inch rise needs at least a 288-inch (24-foot) run to meet the 1:12 ADA maximum, a widely cited reference figure this calculator reproduces exactly — so you can see how much horizontal space each standard actually requires, not just whether your specific ramp passes or fails.

FAQ

Is 1:12 always the maximum allowed slope?

1:12 is the ADA's maximum for a standard new ramp run under the federal accessibility standard, but local building codes, existing-facility exceptions, and other jurisdictions' rules can differ or add further requirements (like maximum rise per run before a landing is required, or handrail rules) — always confirm against the specific code that applies to your project rather than relying on this alone.

Why does a gentler slope matter if 1:12 is already compliant?

1:12 is a legal maximum, not necessarily a comfortable one — for a person self-propelling a manual wheelchair, the physical effort to climb a 1:12 ramp is meaningfully higher than a 1:16 or 1:20 ramp of the same rise, which is why accessibility guidance encourages a gentler slope whenever the available space allows it.

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