Calculators
Stair Calculator
Calculate the number of risers, riser height, treads, total run and stringer length for a straight staircase.
- Runs in your browser
- Nothing uploaded
The tool
Enter your numbers below. Results update as you type, and nothing leaves your browser.
Everything you enter stays on your own machine. Nothing is sent to us or to anyone else, which you can confirm in your browser network tab.
What people use it for
- Laying out stair stringers
- Checking stair code compliance
- Planning a loft or basement stair
- Estimating stair materials
About this tool
What the Stair Calculator does
Comfortable, code-compliant stairs divide the total rise into equal risers no taller than the code maximum, with treads deep enough to walk on safely. In the US residential code, risers are typically at most 7¾ inches and treads at least 10 inches. This calculator lays out a straight run.
It also works as a stair riser tread calculator or a stair stringer calculator.
Formula
- Risers = total rise ÷ maximum riser (rounded up)
- Riser height = total rise ÷ risers
- Treads = risers − 1; total run = treads × tread depth
- Stringer = √(rise² + run²)
Worked example
Using the starting values in the calculator above:
| Input | Value |
|---|---|
| Total rise (floor to floor) | 108 in |
| Maximum riser height | 7.75 in |
| Tread depth | 10 in |
| Result | Value |
|---|---|
| Number of risers | 14 |
| Riser height | 7.71 |
| Number of treads | 13 |
| Total run | 130.0 |
| Stringer length | 14.08 |
| 2 × riser + tread | 25.4 |
| Stair angle | 39.7 |
How to read the result
All risers in a flight must be nearly identical; codes allow only a small variation, because uneven steps cause trips.
Headroom, handrails and nosing also have code requirements; check your local building code.
Quantities are estimates. Check product data sheets and local codes, and confirm with your supplier before ordering.
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Questions
Questions about this tool
The things clients actually want to know — costs, timelines, ownership and what happens after launch.
Divide the total rise by the maximum riser height and round up to get the number of risers.
Under the US International Residential Code it is 7¾ inches; other codes differ.
Twice the riser plus the tread should fall around 24 to 25 inches for a comfortable stair.
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