Category: Calculators
Stair Calculator
Work out risers, treads and stringer length for a staircase
Enter the total rise and a maximum comfortable riser height to calculate the number of steps and the actual riser height, plus tread depth and stringer length if you know the total run.
Total rise and maximum riser height must use the same unit. The calculator rounds up to the fewest risers that keep each step at or below your maximum, then spreads the rise evenly. Tread depth and stringer length only appear once a total run is entered, in that same unit.
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What this tool does
The calculator divides the total rise by your maximum riser height and rounds up to the nearest whole step, so every riser is at or below your limit. It then spreads the total rise evenly across that many risers. If you also enter the total run, it divides that by the number of treads to get the tread depth, and combines rise and run to estimate the stringer length.
How to use it
- Enter the total rise, the vertical height the stairs need to climb.
- Enter the maximum riser height you are comfortable with, or your local building code limit.
- Optionally enter the total run, the horizontal distance the stairs will cover.
- Read the number of risers, the actual riser height, and the tread depth and stringer length if you entered a run.
Privacy
This tool runs entirely in your browser. Your input is never uploaded, stored or shared — closing the tab removes it.
Frequently asked questions
- What is the difference between risers and treads?
- A riser is the vertical part of a step and a tread is the horizontal part you step on; a staircase always has one more riser than treads, since the top step doubles as the landing.
- What riser height should I use?
- Many residential codes cap risers around 7.75 inches (about 19.7 cm), with a comfortable target closer to 7 inches (about 17.8 cm); check your local building code before finalizing a design.
- How is the stringer length calculated?
- As the diagonal of a right triangle formed by the total rise and total run, using the Pythagorean theorem; it estimates the length of lumber needed for each stair stringer before angled cuts.