Stair Calculator
Calculate stair riser height, tread depth, stringer length and angle to building code. Free stair stringer calculator.
IRC limits: risers 4–7 in, 7¾ in max; treads 10 in min. Uniformity matters — a ⅜ in difference between risers is a trip hazard.
Frequently asked questions
- What is the rule of thumb for comfortable stairs?
- Twice the riser plus the tread should land between 24 and 25.5 inches. That combination feels natural to walk.
- How many stringers do I need?
- One on each side plus one centred for stairs wider than 36 inches. Cut from 2×12 lumber for strength.
- Does this account for the finished floor?
- The total rise is measured from finished floor to finished floor. Include flooring thickness before calculating.
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