Enter your deck height to calculate code-compliant stair dimensions, stringer lengths, and a complete materials list for treads, risers, and stringers.
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Divide the total rise (deck height from ground to deck surface in inches) by your target riser height (typically 7 to 7.75 inches). Round up to get the number of risers, then subtract one to get the number of treads. For example, a 48-inch deck height divided by 7.5 inches gives about 7 risers and 6 treads.
The Ontario Building Code and IRC limit the maximum riser height to 7.75 inches (197 mm). The minimum is typically 5 inches. All risers in a staircase must be uniform — the tallest and shortest riser cannot differ by more than 3/8 inch.
Most building codes require stringers spaced no more than 16 inches apart for 2x lumber treads, or 24 inches for engineered treads. For a standard 36-inch-wide staircase, you need 3 stringers. Wider stairs (48–60 inches) typically need 4 stringers.
Stringer length is the hypotenuse of a right triangle formed by the total rise (vertical height) and total run (horizontal distance). Use the formula: stringer length = √(total rise² + total run²). Add 12 inches for the top and bottom connections. Stringers are typically cut from 2×12 lumber.
Ontario Building Code requires a landing for any staircase with a vertical rise exceeding 12 feet. Landings must be at least 36 inches deep (in the direction of travel) and at least as wide as the stairway. Even if not required by code, landings improve safety for stairs with more than 12 risers.
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