This calculator computes ramp slope from rise and run and checks it against the ADA 2010 Standards’ 1:12 accessible-route limit (Section 405.2, matched by IBC Section 1012), including what an existing-building alteration exception could allow when the default limit is not met. It is a reference estimate, not a code determination: confirm the applicable standard and any local amendments with your local building department or accessibility specialist.
Before you use this: what this tool is and is not
This is a reference and estimating tool, not a code determination. It checks the rise and run you enter against the ADA 2010 Standards and the matching IBC ramp provisions. It does not know whether your project qualifies as an existing facility, or whether a local amendment changes these numbers. Confirm the applicable standard with your Authority Having Jurisdiction (AHJ) or an accessibility specialist before you rely on the result.
This page uses the ADA 2010 Standards for Accessible Design, Section 405, and the matching ramp provisions in IBC Section 1012 (2021 and 2024 International Building Code). Vehicle and parking-garage ramps are out of scope — they follow a different provision, not the pedestrian ramp rules used here.
Calculate a ramp’s slope
Ramp slope calculator
For pedestrian means-of-egress and accessible ramps only. Not for vehicle or parking-garage ramps.
The limits this tool checks
Per the U.S. Access Board’s guide to ramps and curb ramps and the ADA 2010 Standards, Section 405 (both accessed 2026-09-17), matched on the building-code side by IBC’s ramp requirements under Section 1012 (accessed 2026-09-17):
| Ramp type | Maximum running slope | Other limits |
|---|---|---|
| Accessible / egress ramp (ADA 405.2, IBC 1012) | 1:12 (8.33%) | Cross slope 1:48 (2.08%) max; 30 in max rise per run before a landing; landings at least 60 in × 60 in; handrails required when rise exceeds 6 in; clear width at least 36 in between handrails |
| Other pedestrian ramp, not on an accessible or egress route (IBC 1012) | 1:8 (12.5%) | Does not satisfy the accessible-route requirement |
| Existing-facility alteration exception (ADA Table 405.2) | Steeper than 1:12, up to 1:10 | Maximum rise 6 in for that run |
| Existing-facility alteration exception (ADA Table 405.2) | Steeper than 1:10, up to 1:8 | Maximum rise 3 in for that run |
Nothing steeper than 1:8 is ever allowed under any exception. Vehicle and parking-garage ramps follow a different provision and are not covered by this page.
Where Groundbook fits
Groundbook can compare the accessible-route information shown on your drawings — including ramp slope, routes, doors, and level changes — against the accessibility code or reference material you supply for the review, and flag places where the documents disagree or a requirement does not carry through; see the accessibility plan review checklist. It does not certify ADA compliance, and it does not compute slope for you the way this calculator does — use this tool first, then have Groundbook check the drawn dimensions against your uploaded code sources.