How to Use the Stair Riser Calculator
Before you can order stringers, risers, or treads, you need to decide how many steps a staircase will have and how tall each riser is. This calculator takes the total floor-to-floor height and your target riser height, then tells you how many risers are needed and what the actual, evenly distributed riser height comes out to.
The calculation rounds the floor height divided by your target riser height up to the next whole number of risers, then redistributes the full floor height evenly across that many risers. Floor heights almost never divide evenly into a clean riser height, so this even-distribution step is what keeps every step in the run exactly the same size — critical for preventing trip hazards.
Under the IRC (R311.7.5.1) and IBC (1011.5.2), maximum riser height is generally 7.75 in and minimum tread depth is 10 in for most stairs. This calculator also suggests a tread depth using the common carpentry rule of thumb 2 x riser + tread = 25 in, but code minimums and final dimensions should always be verified with a licensed architect, engineer, or your local building department before construction.
Frequently Asked Questions
The International Residential Code (IRC R311.7.5.1) and International Building Code (IBC 1011.5.2) cap riser height at 7-3/4 inches (7.75 in) for most stairs, which is why it's the standard default in practice. Requirements can vary by occupancy type, so always confirm with your local code before finalizing.
It rarely does. This calculator rounds the riser count up, then redistributes the total floor height evenly across that many risers, so every riser ends up exactly the same height.