Stair Calculator
Riser count, riser height, tread depth and stringer length — with a code check.
What is Stairs?
Stairs are designed by choosing the *count* first: the riser count is the whole number that lands closest to a comfortable target (7–7.5 inches), and every riser is then exactly totalRise ÷ count — which is what keeps steps even, because a flight whose risers vary by more than ⅜ inch is a trip hazard, not a design choice. The count, not the height, is the input you tune. Treads come from the run: total run ÷ (count − 1), checked against the 10-inch minimum.
How it works
Risers = round(rise ÷ target). Riser height = rise ÷ risers. Tread = run ÷ (risers − 1) when the run is given. The stringer is the hypotenuse of the rise over the run. Compliance is flagged against the limits you enter (the IRC's 7¾-inch riser and 10-inch tread are the defaults), with the reason spelled out — a non-compliant stair is named as such, not silently accepted.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
Nothing is uploaded — every tool in this category runs entirely in your browser.