Stair Calculator
Estimate risers, treads and stringer length for any staircase.
Stair layout starts with total rise: divide rise by a target riser of about 7 inches and round to a whole number of risers. Treads equal risers minus one. Keep risers 7–7.75 inches and treads 10–11 inches so that 2 × riser + tread lands near 25 inches. Enter your total rise and run for a full stringer layout.
How does the stair calculator work?
Divide total rise by the maximum riser height (IBC 7.75 in) and round up to get the number of risers. Riser height = rise ÷ risers. Treads = risers − 1. Total run = treads × tread depth. Stringer = √(rise² + run²).
Which guide explains this in more depth?
- Riser-and-tread math plus 2026 material prices for a full stair build. Read the stair calculator cost breakdown guide for the full worked example.
What else do people ask about this calculator?
What is the maximum stair riser height?
IBC allows 7.75 in max; IRC (residential) allows 7.875 in. Minimum tread depth is 10 in (11 in for IBC commercial).
How long is a stair stringer?
For a 108 in rise and a 10 in tread, stringer length is √(108² + 130²) ≈ 169 in (14.1 ft). Order 16 ft stringers.
Which related calculators should I use next?
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