Stair Calculator
Turn a floor-to-floor rise into a riser height, a tread count, and the horizontal run. Check the result against the local stair rules before you cut.
Use it when you know the total rise and want an even riser, tread, and run.
Compare scenarios
How we calculated this
The count of risers starts by dividing the total rise by the target riser and rounding. If a riser would be taller than 7.75 inches, another riser is added. There is one fewer tread than risers. Total run is treads times tread depth. Stringer length is the straight-line distance along the rise and run.
What does this mean?
Use 14 risers at 7.71 inches, and 13 treads. The stair runs 10.83 feet.
Your assumptions
Edit assumptions- Total rise
- 108.00 in
- Target riser
- 7.50 in
- Tread depth
- 10.00 in
Stair dimensions are regulated locally. This estimate targets common residential limits and is not a code approval.
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How the estimate is calculated
Risers start from the total rise divided by a 7.5 inch target.
If a riser would exceed 7.75 inches, another riser is added. There is one fewer tread than there are risers.
Stair layout
Riser height = total rise ÷ number of risers. Total run = (risers − 1) × tread depth. Stringer length is the diagonal of the rise and the run.
Example
- Measure from finished floor to finished floor in inches, including the floor thicknesses you will actually have.
- Keep a 7.5 inch target unless you are matching an existing stair.
- Use at least a 10 inch tread unless a design constraint forces otherwise.
With the numbers filled in on this page, the estimate is 7.71 inches.
What changes the result
Code
A common residential maximum riser is 7.75 inches and a common minimum tread is 10 inches. Local rules can be stricter.
Finished sizes
Carpet, tile, and the nose of the tread change the finished dimension. Measure the surfaces you will walk on.
Landings
This is one straight flight. A landing resets the rise for the next flight.
Questions
Why are there fewer treads than risers?
The top step lands on the upper floor, so that surface is not a tread you build.
What is the stringer length?
It is the straight distance along the stair, from the rise and the run. It does not add waste for cuts.
Can I use this for deck stairs?
As a first layout, yes. Confirm outdoor stair rules, which can differ.