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For residential stairs in the U.S., the standard rise per step is 7 to 7¾ inches and the standard run (tread depth) is 10 to 11 inches. IRC code requires a maximum riser height of 7¾ inches and a minimum tread depth of 10 inches. The widely cited 7-11 rule — 7-inch rise, 11-inch run — produces the most comfortable walking cadence and a stair angle around 32°.

OSHA’s general industry stair standard (29 CFR 1910.25) requires risers between 6¾ and 9½ inches and treads at least 9½ inches deep (minimum 11 inches for new construction). All risers in a flight must be uniform within ⅜ inch, and stairs serving workers must include handrails on open sides plus adequate landing clearance at the top and bottom.

Divide the total rise (floor-to-floor height) by your target riser height to find the number of steps. For example, 108 inches of total rise divided by a 7.5-inch target riser = 14.4 steps — round to 14 steps at a slightly taller rise (7.71″) or 15 steps at a slightly shorter rise (7.20″). Always adjust the riser height so the total rise divides evenly into the step count.

Stringer length is calculated using the Pythagorean theorem: Stringer Length = √(Total Rise² + Total Run²). For example, a staircase with a 106-inch total rise and 140-inch total run has a stringer length of √(106² + 140²) = √30,836 ≈ 175.6 inches (about 14.6 feet). Always add 6–12 inches of extra length when ordering material to allow for top and bottom cuts.

The 7-11 rule states that residential stairs are most comfortable when each step has a 7-inch rise and 11-inch run. This combination creates a stair angle of approximately 32°, which matches the natural walking cadence of most adults. It’s a comfort guideline, not a strict code — IRC code allows risers up to 7¾ inches and treads as shallow as 10 inches.

In a standard mount, the bottom step’s rise equals the rise per step — the stringer sits on top of the lower floor and the first tread is one full step above it. In a flush mount, the bottom step’s rise equals the rise per step minus the tread thickness — the stringer attaches to the side of the lower floor and the first tread sits at the same height as the floor surface. Flush mount is more common when the staircase needs to align with finished flooring at the bottom.

Residential stairs should have a stair angle between 30° and 38° for comfort and code compliance. The IRC effectively caps the angle around 37–38° using its maximum 7¾-inch rise and minimum 10-inch tread. Anything steeper qualifies as a “ladder stair” or “alternating tread device” and falls under different code provisions, with additional handrail and clearance requirements.

IRC code requires residential stairs to be at least 36 inches wide measured above the handrail, with a minimum 27-inch clear width between handrails when handrails are installed on both sides. Commercial and code-compliant exit stairs typically require 44 inches or more. Always confirm width requirements with your local AHJ before framing the opening.