Building stairs to code means getting the rise, run, and number of treads right. This calculator takes your total floor-to-floor height and gives you code-compliant stair dimensions that are safe and comfortable to walk on.
Staircase Dimensions
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Scenario: Your floor-to-floor height is 108 inches (9 ft), you want a target riser height of 7.5 inches, and a tread depth of 10.5 inches.
Result: 108 / 7.5 = 14.4, rounded to 14 risers. Actual riser height: 108 / 14 = 7.71 inches. With 13 treads at 10.5 inches deep, total run is 136.5 inches (11.4 ft). Stringer length is about 14.5 ft.
Building code (IRC) limits risers to a maximum of 7.75 inches and a minimum of 4 inches. The most comfortable range is 7 to 7.5 inches. All risers in a staircase must be within 3/8 inch of each other.
An 8-foot ceiling works out to about 105 inches floor-to-floor (96 in ceiling + ~9 in floor structure). At 7.5-inch risers, that's 14 risers and 13 treads, requiring about 11.5 feet of horizontal run.
The 7-11 rule says risers should be about 7 inches tall and treads about 11 inches deep. More precisely, codes require the riser + tread combination to fall between 17 and 18 inches total for comfort and safety.
Multiply the number of treads by the tread depth. For a standard 13-tread staircase with 10.5-inch treads, you need 136.5 inches (about 11.5 feet) of horizontal run, plus a landing at top and bottom.
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