Stair Calculator: Rise, Run & Stringer Layout
Calculate the rise, run, and stringer length for building stairs.
The Math Behind Stairs
Building stairs requires precise calculations to ensure every step is the exact same height. A difference of even 1/4 inch can be a tripping hazard and a code violation.
Calculating Unit Rise
- Measure the Total Rise from finished lower floor to finished upper floor.
- Divide Total Rise by 7 (the standard step height).
- Round the result to the nearest whole number to get the Number of Steps.
- Divide the Total Rise by the Number of Steps to get the exact Unit Rise.
Stair Building FAQs
What is the standard rise and run?
The '7-11' rule is standard: a 7-inch rise and an 11-inch run. Most codes strictly limit the maximum rise to 7.75 inches.
What is a stringer?
The stringer is the structural board (usually 2x12) that is cut to support the treads and risers.