Staircase Dimension & Code Compliance Calculator
Calculate the exact number of risers, treads, and total run for a staircase from its floor-to-floor height, and check the result against common US residential (IRC) and commercial (IBC) building code thresholds.
Enter your floor-to-floor height to calculate the exact number of risers and treads, the total run, and check the result against common US residential (IRC) and commercial (IBC) building code thresholds.
How This Calculator Works
A staircase can't have a fractional step, so the calculator starts from your target riser height, divides it into the total floor-to-floor height, and rounds to the nearest whole number of risers. It then recalculates the exact riser height as total rise ÷ number of risers — this is why the final riser height is usually slightly different from the target you entered, and why every riser in a code-compliant flight must be equal, within a very small tolerance.
A staircase with N risers has N − 1 treads, because the final riser lands on the upper floor itself rather than another step. Total run is the number of treads multiplied by the tread depth — the total horizontal distance the staircase covers, not counting any landing.
The two most-cited US model codes set different limits: the IRC (International Residential Code, used for one- and two-family homes) allows a maximum riser of 7¾ in (196.85 mm) and a minimum tread of 10 in (254 mm), while the IBC (International Building Code, used for commercial and multi-family buildings) is stricter — a maximum riser of 7 in (178 mm) and a minimum tread of 11 in (279 mm). Local jurisdictions often adopt these codes with amendments, so always confirm the exact figures with your local building department.
First proposed by French architect François Blondel in 1675, the formula 2 × riser + tread is still widely used as a quick comfort check — a result between 24 and 25 inches (610–650 mm) is considered a comfortable, natural stride. It's a design guideline, not a legal requirement, but stairs that fail it badly often feel awkward to climb even when they technically meet code.
Frequently Asked Questions
About this calculator
This calculator turns a single measurement — the floor-to-floor height — into a complete staircase layout: the exact number of risers and treads, the recalculated riser height that makes them all equal, the total horizontal run, and the diagonal stringer length. It then checks that layout against the two most-cited US model building codes (IRC and IBC) and the classic Blondel comfort formula, and draws a proportionally scaled side-view diagram with the key measurements labeled.
- Whole-number riser solving — Automatically rounds to a whole number of risers from your target height, then recalculates the exact riser height so every step in the flight is equal.
- IRC and IBC compliance checks — Checks your calculated riser height and tread depth against both the US residential (IRC) and commercial (IBC) model code thresholds at once.
- Headroom and width checks — Also checks the headroom clearance and stair width you enter against commonly cited minimums.
- Blondel comfort formula — Flags whether your riser-and-tread combination falls inside the classic 24–25 in (610–650 mm) comfort range used by architects since the 17th century.
- Scaled 2D stair profile — Draws a proportionally scaled side-view diagram of your staircase with the total rise, total run, riser height, and tread depth labeled.