Work out the minimum accessible ramp run for a given total rise, per the 2010 ADA Standards for Accessible Design, Section 405. Enter the total rise and the calculator gives the minimum run length at the maximum allowed 1:12 slope, the number of intermediate landings required (ramps are limited to a 30 in rise between landings), the minimum landing size, and whether handrails are triggered.
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ADA 2010 is a federal civil-rights minimum — state accessibility codes (e.g. California Title 24/CBC Ch. 11B, Texas Accessibility Standards) can be stricter and must be checked separately. The 1:10/1:8 steeper slopes are an existing-building alteration exception only, not a new-construction option. Curb ramps (§406) and vehicular ramps have separate rules not covered here.
How the calculation works
- Minimum run. Total rise × 12, giving the shortest run that keeps the ramp at or below the maximum 1:12 slope for new construction (steeper 1:10 and 1:8 slopes are only permitted as limited alteration exceptions with lower maximum rise).
- Landings. A level landing at least 60 in long is required at the top and bottom of every ramp run, and wherever the rise reaches the 30 in-per-run maximum.
- Handrails. Required on both sides whenever the rise exceeds 6 in.
- Cross slope. Must not exceed 1:48, regardless of the running slope.
What to have ready
- Total rise the ramp needs to climb
- Whether this is new construction or a documented alteration (which may allow a steeper slope over a shorter rise)
- Available clear width for the ramp
Notes and limitations
This tool covers ADA Standards ramp geometry (slope, run, landings, handrail trigger) only — it does not check surface texture/traction, edge protection, handrail height and graspability details, or wet-condition slip resistance, all of which are also required. Some state and local accessibility codes are more restrictive than the federal ADA Standards; always check the code adopted in your jurisdiction. Final acceptance of the design rests with the responsible design professional.
ADA Ramp Design Reference Table — ADA Standards 405
| Parameter | ADA Requirement | ADA Section | Notes |
|---|---|---|---|
| Maximum slope | 1:12 (8.33%) | 405.2 | 1 in of rise per 12 in of run |
| Maximum cross slope | 1:48 (2.08%) | 405.3 | Perpendicular to direction of travel |
| Minimum clear width | 36 in (915 mm) | 405.5 | Between handrails |
| Maximum rise per run | 30 in (760 mm) | 405.6 | Landing required between each 30 in of rise |
| Landing size (top/bottom) | 60 × 60 in min | 405.7 | At top, bottom, and each change of direction |
| Landing slope (max) | 1:48 in all directions | 405.7.1 | Landings must be essentially level |
| Handrail height | 34–38 in | 405.8 / 505.4 | Measured vertically from ramp surface |
| Handrail gripping surface | Circular: ⌀ 1¼–2 in | 505.7 | Non-circular: 4–6¼ in perimeter |
| Handrail extension (top) | 12 in beyond top | 505.10.2 | Must return to post, wall, or floor |
| Edge protection | Curb ≥2 in or barrier | 405.9 | Required on open sides of ramp runs and landings |
Source: 2010 ADA Standards for Accessible Design, Chapter 4 (Accessible Routes), Sections 405 and 505.
ADA Ramp Slope & Length Calculator FAQ
What is the maximum ADA ramp slope?
The maximum slope for an ADA-compliant ramp is 1:12 — one inch of vertical rise for every 12 inches of horizontal run — per ADA Standards Section 405.2. This equals approximately 8.33% grade or 4.76 degrees. For existing sites where space is limited, the ADA allows steeper slopes as exceptions: 1:10 (10%) for rises up to 6 inches, and 1:8 (12.5%) for rises up to 3 inches, but only where space limitations prevent 1:12 compliance. New construction must always use 1:12 or flatter. Curb ramps in the public right-of-way must comply with PROWAG (Public Rights-of-Way Accessibility Guidelines), which also requires 1:12 or flatter slopes.
How long must an ADA ramp be to rise 12 inches?
At the maximum 1:12 slope, an ADA ramp must be at least 12 inches long for every 1 inch of vertical rise. To rise 12 inches, the ramp run must be at least 144 inches (12 feet). ADA Section 405.6 limits each ramp run to a maximum rise of 30 inches — meaning the maximum continuous run length is 30 × 12 = 360 inches (30 feet) before a landing is required. For a total rise of 30 inches at 1:12 slope: ramp run = 360 in (30 ft) + two 60×60-inch landings at top and bottom.
Does every ramp need handrails on both sides?
Yes — ADA Standards Section 405.8 requires handrails on both sides of ramp runs where the rise exceeds 6 inches or the horizontal projection exceeds 72 inches. Handrails must be continuous for the full length of the ramp run (405.8), extend 12 inches beyond the top landing (505.10.2), and return to a post, wall, or floor at the bottom. The gripping surface must be between 34 and 38 inches above the ramp surface (405.8 / 505.4). Ramps with less than 6 inches of rise are not required to have handrails, but edge protection per 405.9 is still required.
What is the difference between a ramp and a curb ramp under ADA?
A ramp (ADA Section 405) is an inclined walking surface with a slope steeper than 1:20 in an accessible route, typically used to transition between floor levels inside a building or between grades. A curb ramp (Section 406) is a built-up inclined surface or depression cut through a curb to provide access at a street crossing or between a sidewalk and a vehicular way. Curb ramps must also not exceed 1:12 slope and must include detectable warning surfaces (truncated domes per 705) at the bottom, which are not required on interior or exterior building ramps.
Can I use a steeper slope than 1:12 if it’s a residential project?
The ADA applies to places of public accommodation and commercial facilities — not private residences. However, the Fair Housing Act (FHA) requires accessible design features in covered multifamily housing (4+ units in buildings with elevators, or ground-floor units in non-elevator buildings), but FHA does not specify ramp slope limits as explicitly as ADA does. The IRC (International Residential Code) allows exterior ramps up to a 1:8 slope for single-family dwellings. If the project serves the public in any capacity — a home-based business, rental units — ADA requirements may apply. Always confirm jurisdiction-specific requirements with your local building department.