Stair Calculator
Riser height, tread run, and stringer length for a staircase.
Steps
14
riser 7.71" · tread 9.6"
Total run
10.4 ft
Stringer length
13.7 ft
IRC code check
Adjust riser/tread to meet code
The comfort formula
Carpenters size stairs so 2×riser + tread ≈ 25 inches — matching the human stride. A 7.5" riser pairs with a 10" tread. Total rise ÷ target riser, rounded to a whole step count, sets the actual riser; every step must be equal within ⅜" by code.
Code is the floor, not the goal
The IRC caps risers at 7¾" and floors treads at 10", but slightly gentler stairs (7"/11") measurably reduce falls. The last riser includes finish-floor thickness — forgetting flooring height is the classic first-timer's uneven top step.
Related calculators
Age Calculator
Calculate exact age in years, months, and days between two dates.
Date Calculator
Add or subtract days from a date, or count days between dates.
Hours Calculator
Count hours between two times — great for timesheets.
GPA Calculator
Calculate your GPA from course grades and credit hours.