Stair Calculator
Calculate step count, rise, run, stringer length and angle for any staircase.
How the Stair Calculator Works
This stair calculator uses your total rise — the vertical distance from floor to floor — and your preferred rise per step to compute the number of steps needed. It divides the total rise by the desired rise, rounding up to the nearest whole step, then back-calculates the actual rise per step so all steps are perfectly even. The stringer length is calculated using the Pythagorean theorem: the square root of (rise² + run²) multiplied by the number of steps. The stair angle is the arctangent of rise over run, converted to degrees. Building codes (IRC Section R311) specify a maximum rise of 8.25 inches and a minimum tread depth of 9 inches for residential stairs. Always verify your local code before building.