What is the maximum stair riser height?
For stairs in one- and two-family dwellings the maximum riser height is 7¾ inches (7.75 in) under the 2018 IRC (§R311.7.5.1). The tallest and shortest riser in a single flight may differ by no more than 3/8 inch, so risers must be evenly spaced.
Source: 2018 IRC §R311.7.5.1 · Verify against your AHJ and the adopted code edition.
The riser is the vertical face of each step. In a home, the IRC limits it to 7¾ inches so the stair isn’t dangerously steep.
Just as important as the maximum is the uniformity rule: within one flight, the difference between the tallest and shortest riser can’t exceed 3/8 inch. Uneven risers are a leading cause of stair falls because your body learns the rhythm of the first step and expects every step to match. This is why you size a stair by dividing the total floor-to-floor height into equal risers rather than eyeballing a “7-inch” step.
Commercial stairs are stricter. Under the IBC, the maximum riser is 7 inches (§1011.5.2). Occupancy, existing-building provisions, and local amendments all change the details — always confirm against your adopted code and authority having jurisdiction (AHJ).
Work it out: enter a floor-to-floor rise in the stair calculator and it finds the number of risers that keeps each one at a comfortable, code-compliant height, then reports the exact riser height, tread run, and pitch.
Sources
- ICC — International Codes (IRC) — 2018 IRC §R311.7.5.1