Stair Calculator

A staircase needs a whole number of equal-height steps — you can't build 15.43 risers — so the calculator rounds your target riser height to the nearest whole number of risers, then recalculates the actual riser height so all risers in the finished staircase are exactly equal (a critical safety requirement, since uneven riser heights are a major trip hazard).

Most residential building codes cap riser height around 7-7.75 inches, with many codes also requiring a minimum tread depth (commonly 10 inches) — check your local building code for exact requirements, since they vary by jurisdiction and stair type (interior vs. exterior, for example).

Each riser represents a vertical step up, while treads are the horizontal surfaces you walk on between risers — a staircase with the floor itself counting as the top "step," so a 15-riser staircase has only 14 physical tread boards, with the 15th "step" being the upper floor landing itself.

Total run is the total horizontal floor space the finished staircase will occupy (number of treads × tread depth) — a critical number for planning whether a staircase will physically fit in the available space before construction begins.