Stair Calculator
Plan a staircase from your total rise — get the number of steps, the exact riser height, the total run and the stringer length, with a note on code limits.
Stair Calculator
Runs in your browser — nothing you enter is uploaded or stored.
Scratchpad auto-saved
How it works — in four simple steps
No signup and nothing to install — it all runs in your browser.
Measure the total rise
Measure the vertical distance from the lower floor to the upper floor, in inches, and enter it.
Set your targets
Enter a comfortable target riser height (around 7 inches) and your tread depth (10–11 inches is typical).
Calculate
See the number of steps, exact riser height, total run and stringer length.
Check the code note
Confirm the riser and tread are within your local building code before you build.
US residential code (IRC) caps risers at 7¾″ with treads of at least 10″ — and stairs feel best when 2 × riser + tread ≈ 25″.
Features
Even risers, every time
Enter the total rise and the tool divides it into a whole number of equal risers close to your target height — the key to a safe, comfortable stair.
Full step geometry
Get the riser height, number of treads, total run and the diagonal stringer length in one calculation.
Stringer length included
The stringer (the angled support board) is worked out with the Pythagorean theorem, so you know the board length to buy.
Code check built in
The result flags whether your riser and tread fall within the common 7¾″ / 10″ building-code guide.
About the Stair Calculator
Designing a staircase starts from the total rise — the vertical distance from one finished floor to the next. You divide that rise into a whole number of equal risers (the vertical face of each step), because every step must be the same height for the stair to be safe and comfortable.
This calculator takes your total rise and a target riser height (7 inches is a comfortable default), finds the nearest whole number of even risers, and works out the exact riser height. From there it derives the number of treads (always one fewer than the risers), the total run (treads × tread depth), and the stringer length — the diagonal board that carries the steps, found with the Pythagorean theorem: √(rise² + run²).
It also flags whether your design falls within a common building-code guide — a maximum 7¾-inch riser and a minimum 10-inch tread (US IRC) — though you should always confirm your local code. Everything is calculated in your browser.