What Is the Stair Height Calculator?
Every stair calculation starts with one number: the total height from the finished lower floor to the finished upper floor. Our free stair height calculator turns that single measurement into the numbers that drive the whole design: how many steps you need, the exact uniform height of each step, and whether the resulting stair keeps enough headroom to pass inspection. Measure the total rise, enter it, and set your target step height. The calculator rounds to a whole number of steps, then recalculates the precise riser height so no step is taller or shorter than the rest, and checks it against the 7.75-inch IRC maximum. An optional headroom check tells you whether the stair angle your height produces still leaves the required 80 inches of clearance above the treads. That matters because a stair with perfect step heights can still fail inspection if the geometry eats into the headroom. Use it for interior stairs, deck stairs, basement stairs, and porches: anywhere you need to know, from one measurement, whether the stair you are planning will actually fit and pass.
How to Use This Calculator
- Measure the total rise from the finished lower floor to the finished upper floor, in inches.
- Enter your target step height (riser). Comfortable stairs typically use 7 to 7.5 inches.
- Review the calculated number of steps and the exact riser height, which the calculator recalculates so every step is uniform.
- Confirm the riser height is at or below the 7.75-inch IRC maximum for residential stairs.
- Enter the available headroom above the stair if you want a clearance check against the 80-inch minimum.
- If the riser comes out above the limit, increase the step count by one and let the calculator recompute a shorter, compliant riser.
- Export the results as a PDF for your cut list or inspector.
