Calculators/ Framing & Exterior/Stair Stringer Calculator
Stair Stringer Calculator
Rise, run and stringer length for wooden stairs.
Stair Stringer Calculator
in
in
in
in
Stair layout starts from the total rise and works backwards. The riser count has to divide the rise evenly, because an uneven step at top or bottom is both a code violation and the classic cause of a trip.
How this is calculated
- Divide the total rise by your preferred rise and round to the nearest whole number. That is the riser count.
- Divide the total rise by that count for the exact rise. It will rarely be a round number, and every step must use it.
- Treads are one fewer than risers when the top step is the landing. Total run = treads × tread run.
- Stringer length is the diagonal: √(rise² + run²). Buy stock at least a foot longer to allow for the cuts.
Frequently asked questions
What is the maximum stair rise?
Most US residential code caps riser height at 7¾ inches and requires a minimum 10 inch tread. Variation between steps in a single flight is limited to 3/8 inch.
Why must every riser be identical?
People climb stairs by rhythm, not by looking. A single step that differs by even half an inch is the most common cause of falls on stairs.