Stair geometry limits under IRC 2018 (US Residential), with the governing clause for each and a worked 9-foot example. Then run your own numbers in the calculator.
IRC 2018 is the residential stair baseline still enforced in many US jurisdictions that have not yet adopted a newer cycle. Its stair geometry sits in Section R311.7, and the dimensional limits below are identical to the 2021 edition — the practical reason to care which edition applies is the clause numbering your inspector will cite, not the numbers themselves.
| Requirement | Limit | Clause |
|---|---|---|
| Max riser height | 7.75″ | R311.7.5.1 |
| Min tread depth | 10.0″ | R311.7.5.2 |
| Min stair width | 36.0″ | R311.7.1 |
| Min headroom | 80.0″ | R311.7.2 |
| Max rise between landings | 147.0″ | R311.7.6 |
For a 108-inch total rise under IRC 2018 (US Residential): dividing by the 7.75-inch maximum riser gives a minimum of 14 risers. Spreading 108 inches evenly across 14 risers yields 7.71 inches per riser — within the limit and uniform, as the code requires.
Run your stair against IRC 2018 (US Residential)
In the 2018 IRC the maximum vertical rise between landings appears at clause R311.7.6. (The 2021 edition kept the same 147-inch limit but renumbered this clause to R311.7.3 as part of a section cleanup.) If your local building department is on the 2018 cycle, cite R311.7.x for stairways — the wholesale move to R318.7 did not happen until the 2024 edition.
Because the dimensional envelope is unchanged from 2018 through 2024, a stair that passes here passes the geometry checks in all three editions. What varies between editions is clause numbering and a handful of landing and nosing refinements introduced in 2024, covered on the IRC 2024 page.
Compare with IRC 2021, IRC 2024, IBC, UK Approved Document K, Australia NCC / BCA, Eurocode / EN.