Stair Calculator — Risers, Treads & Stringer Length

How the stair calculator works

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).

Frequently asked questions

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.

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