Stair Calculator
Calculate the number of steps, riser height, tread depth and stringer length for a staircase given total rise.
- Your Riser Height7.2 in
- Code Max Riser7.5 in
Each step's riser (7.2 in) comes in under your 7.5 in code limit — steps are spread evenly so no single riser exceeds it.
- Riser Height7.2 in
- Total Run140 in
- Stringer Length14.73 ft
About the Stair Calculator
This calculator works out how many steps a staircase needs, how tall each riser will be, and how long the stringer (the diagonal cutting board the treads attach to) needs to be — starting from just the total vertical rise, the tread depth you want, and a maximum riser height limit.
It's built for the moment before cutting stringers on a deck, porch, shed or basement staircase: measure the total height the stairs need to climb, and the calculator spreads that rise evenly across the fewest steps that keep every riser under your code limit.
Getting riser height even and consistent matters more than it might seem — a staircase where one step is noticeably taller or shorter than the rest is a well-documented tripping hazard, which is exactly what evenly dividing the total rise avoids.
How it’s calculated
The calculator first figures out the minimum number of steps needed so that no single riser exceeds your maximum riser height, then divides the total rise evenly across that many steps — this is what keeps every riser exactly the same height rather than leaving an odd, mismatched last step.
Total run is the tread depth multiplied by one fewer than the number of steps (since the top step's edge is level with the landing, not a separate tread). Stringer length is then found with the Pythagorean theorem, treating rise and run as the two legs of a right triangle: stringer = √(rise² + run²).
Frequently asked questions
What's a typical maximum riser height allowed by code?
Most US residential codes cap riser height around 7 to 7.75 inches, though the exact limit varies by jurisdiction — check your local building code before finalizing a design, especially for anything requiring a permit.
Why does the calculator sometimes give a riser height lower than my code maximum?
Because it needs a whole number of steps to divide the total rise evenly, the actual riser height is often a bit under the maximum you entered — for example, a rise that doesn't divide evenly by 7.5 inches will land on a slightly smaller, consistent riser height instead.
What's a comfortable tread depth for outdoor stairs?
10 to 11 inches is a common comfortable range for exterior stairs, giving enough room for a full foot placement; indoor stairs are sometimes built shallower due to space constraints, but shallower treads generally feel less comfortable to walk.
How is stringer length different from total rise?
Stringer length is the diagonal length of the board that supports the stairs — always longer than the vertical rise alone, since it also has to span the horizontal run. That's why it's calculated with the Pythagorean theorem rather than just using the rise.
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