Stair Stringer Length
Also known as stringer length · stair carriage length
Worked example: 3 m rise, 4 m run → 5 m stringer — press Try an example to run it live, then adjust anything.
Enter your known values, leave one input blank, and solves for the missing one. Tap a variable’s symbol to see what it means, with a typical value. Try different units for next level excitement!
Stair Stringer Length explained
The stringer is the hypotenuse of the whole flight, so with the total rise and the total run as the legs. An 8 ft rise over a 10 ft run needs a stringer just over 12 ft 9 in on the diagonal, which tells you at once that a 12 ft 2x12 will not do the job and you are buying a 14 footer.
Two practical cautions. This is the line length along the back of the notches, so the actual board must be longer to allow for the plumb cut at the top, the seat cut at the bottom, and the material left below the notches. Framers usually want at least 3 in of solid wood under every notch, or the stringer becomes a row of sawteeth waiting to split. And do not confuse this length with the handrail length, which follows the nosing line and starts and stops in different places.
Stair Stringer Length formula
- = Stringer length (m)
- = Total rise (m)
- = Total run (m)
Missing one of these? Work it out first, then come back
- Stringer length — Rectangle Perimeter, Rectangle Diagonal
- Total rise — Stair Riser Count from Total Rise, Ground Distance on a Slope
- Total run — Stair Total Run from Risers and Tread Depth, Drain Line Fall from Slope and Run