Home › Free tools › Stair Stringer Calculator
Free calculatorNo signupShort answer: Divide the total rise by 7.75 inches, the IRC maximum riser height, and round up to get the number of risers. Treads are one fewer. A 36-inch rise needs 5 risers of 7.2 inches and 4 treads. With 10-inch treads the run is 40 inches and each stringer is about 54 inches long.
Runs in your browser. Estimates only: check local code and your supplier.
Risers = total rise ÷ max riser (7.75 in), rounded up
Riser height = total rise ÷ risers
Treads = risers − 1 (the deck or landing is the top step)
Total run = treads × tread depth
Stringer length = √(rise² + run²)
Limits from the 2015 IRC (R311.7.5) and the AWC DCA 6 deck guide: risers no taller than 7¾ in, treads at least 10 in, risers within ⅜ in of each other, stringers cut from 2×12, at least 3 cut stringers spaced no more than 18 in apart, and cut stringers spanning no more than 6 ft horizontally. Your local code may differ.
Total rise 36 in, 10-in treads, 36-in-wide stairs:
All 7 paid HandyStack tools, including quotes, materials, invoices, rates and decks, for one price ($123 if bought separately). Save jobs, brand your quotes and stop re-typing numbers.
Measure straight down from the top of the deck surface to the finished ground or landing where the bottom step will sit. If the ground slopes, measure at the spot where the stairs will land.
Many builders aim for a 7 to 7.5-inch riser with a 10.5 to 11-inch tread. One common check is riser × 2 + tread ≈ 25 inches.
At least 3 cut stringers for a 36-inch stair, spaced no more than 18 inches on center. Composite treads often need closer spacing; check the manufacturer.
Buy stringer stock at least a foot longer than the diagonal length so you have room for the top and bottom cuts.