Stair Calculator
Calculate stair rise, run, number of steps, stringer length, and materials for code-compliant stairs.
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How to Calculate Stairs
Divide total rise by target rise per step and round. Then divide total rise by number of risers for exact rise. Number of treads = risers minus one. Total run = treads times tread depth.
Frequently Asked Questions
What is the ideal rise and run for stairs?
Most building codes worldwide specify 175-190 mm (7-7.5 in) rise and 250-280 mm (10-11 in) run. The general comfort rule: rise + run should equal roughly 430-450 mm (17-17.5 in).
How do I calculate stair stringers?
Divide total height by desired rise to get number of steps. Stringer length equals the hypotenuse: square root of (total rise² + total run²). Use 50 x 300 mm (2x12) timber.