Enter a staircase's total rise and desired riser height to calculate the step count, actual riser height, and recommended tread run.
How to Use the Stair Calculator
Enter the total rise — the full vertical height the staircase needs to climb — and a desired riser height to start from. The calculator returns the actual step count and riser height, plus a recommended tread run based on that riser.
The "desired" riser height is really a starting target, not the number the stairs end up with. Total rise almost never divides evenly by a chosen riser height, so the calculator rounds to the nearest whole number of steps and recalculates the riser from there.
number of steps = round(total rise ÷ desired riser height)
actual riser height = total rise ÷ number of stepsThis isn't a cosmetic rounding choice. Building code virtually everywhere requires every riser in a single flight to be the same height, typically within about 3/8 inch of each other — and for good reason. People climb stairs on autopilot, expecting each step to match the rhythm of the last one; a riser that's noticeably taller or shorter than its neighbors is a well-documented, common cause of trips and falls, precisely because the body doesn't consciously check.
The 24–25 Inch Comfort Rule
Once the actual riser height is locked in, tread run follows from a long-standing rule of thumb: twice the riser height plus the run should land around 24 to 25 inches.
recommended run = 25 − (2 × actual riser height)The rule balances two failure modes. A tall riser with a short run feels steep and precarious, forcing an unnaturally short stride. A short riser with a long run feels awkward in the other direction — easy underfoot but wasteful of floor space, and oddly tiring to climb since the stride doesn't match a natural walking gait. Stairs that hit the 24–25 range tend to feel neither.
Actual building codes vary by jurisdiction — check local requirements before cutting any stringers.