Concrete Stairs Geometry Calculator

Enter the total vertical rise and horizontal run, both in meters. The calculator sketches a straight stair with equal risers. It chooses an illustrative count by rounding rise ÷ 0.18 m upward, with a minimum of two risers. The top floor is the landing, so this sketch uses one fewer tread than risers.

Riser height = total rise ÷ riser count. Tread depth = total run ÷ (riser count − 1). The direct rise–run diagonal = √(rise² + run²). These values describe a simple right-triangle sketch; actual nosings, landings, and structure require separate dimensions.

Example: a 2.7 m rise and 3.5 m run give 15 risers at 18 cm each and 14 treads at 25 cm each. The endpoint diagonal is about 4.42 m. A very short rise can yield a riser below 18 cm because the two-riser minimum is only a calculation convention.

This calculator cannot determine concrete volume or weight from rise and run. A solid monolithic stair, an open stair, and a stair on separate stringers may share the same geometry but have different concrete cross-sections. Quantity takeoff needs a selected structure and dimensioned sections; no stringer section is assumed here.

The 2021 International Residential Code §R311.7 is an example of a jurisdiction-specific stair provision covering risers, treads, landings, and related conditions. This tool does not test those conditions, structure, handrails, or which edition applies locally. Source edition: 2021; checked 2026-09-29.