🪜 Stair Calculator
Calculate the number of steps, actual riser height, tread depth, and stringer length for a staircase.
Stair Measurements
Your Result
Most US building codes limit riser height to a maximum of about 7.75 in (19.7 cm) and require a minimum tread depth of about 10 in (25.4 cm). Always check your local building code before construction.
How the Stair Calculator Works
Staircases are designed around a fixed total rise (the floor-to-floor height) divided evenly into a whole number of steps. This calculator finds the number of steps closest to your desired riser height, then recalculates the exact riser height so every step is identical.
Formula
Actual Riser Height = Total Rise / Number of Steps
Tread Depth = Total Run / Number of Steps (or a standard 10 in if no run limit is given)
Stringer Length = √(Total Rise² + Total Run²)
Frequently Asked Questions
What is a comfortable riser height?
Most residential stairs use a riser height between 7 and 7.75 inches (17.8–19.7 cm). Consistent riser heights across all steps are critical for safety.
What is a stair stringer?
A stringer is the diagonal structural board that supports the steps. Its length is the hypotenuse of a right triangle formed by the total rise and total run.