Stair Calculator

Stair layout begins with total rise, the vertical distance from one finished floor level to the next. Dividing this height into equal risers produces a comfortable, consistent flight. This calculator divides the total rise by a selected maximum riser height, rounds the number of risers up to a whole number, and recalculates the exact height of every riser. It then uses one fewer tread than risers for a typical stair ending at an upper floor and multiplies that tread count by tread depth to estimate total horizontal run. Measure total rise between finished surfaces, not unfinished framing, because flooring thickness can change the first or last step. The calculator treats the entered maximum as a limit rather than a target. For example, a 96-inch rise with a 7.75-inch limit requires 13 risers, each about 7.385 inches high. Rounding down to 12 would create 8-inch risers and exceed the selected maximum. Every riser in the finished flight should be substantially equal; even a small variation can create a trip hazard. Tread depth is the horizontal walking surface measured according to the applicable code method. The total run shown here is tread count multiplied by tread depth and does not automatically add landing length, nosing projection, or clearance at either end. Stair geometry also affects stringer length, headroom, guard placement, and the available floor opening. A complete layout must consider all of those constraints together rather than fitting only the rise and run. Building-code requirements differ by location, building type, occupancy, and stair configuration. Codes can regulate maximum riser height, minimum tread depth, variation within a flight, minimum width, landings, handrails, guards, headroom, and nosing details. The default values are planning inputs, not a statement that a design complies. Confirm current requirements with the local authority and project documents before construction. Use the result as a starting point for a scale drawing or full-size layout. Verify the final dimensions against actual site elevations and account for finish materials on floors and treads. Structural stringer sizing, connections, landings, and guards should follow approved plans and material guidance. Where safety or compliance is uncertain, consult a qualified designer, contractor, engineer, or building official.