Stair Stringer Calculator — How Long Do I Cut the Stringers?
Enter your total rise to get the number of steps, rise and run per step, total run, and the exact stringer board length. No sign-up, no data stored.
Stringer plan
How stair stringer length is calculated
- Step count = total rise ÷ target rise per step, rounded up. A 120-in rise at 7.75 in gives 16 steps.
- Actual rise per step = total rise ÷ step count (this keeps every step equal — never leave a big bottom step).
- Total run = run per tread × number of treads (usually one fewer than steps, but simple stairs use steps × run).
- Stringer length = √(total rise² + total run²). A 120-in rise with 160-in run gives √(120² + 160²) ≈ 200 in.
Cut stringers from 2×12 boards (11.25 in actual width) for rises up to about 9 ft. Add 6–12 in to the board length for the top bearing point and any bottom overhang before you buy.
Rise → steps & stringer reference
Framing plan for common total rises at 7.75-in rise and 10-in run.
| Total rise | Steps | Total run | Stringer length | 2×12 board |
|---|---|---|---|---|
| 6 ft (72 in) | 10 | 100 in (8 ft 4 in) | ~123 in | 11 ft |
| 8 ft (96 in) | 13 | 130 in (10 ft 10 in) | ~162 in | 14 ft |
| 10 ft (120 in) | 16 | 160 in (13 ft 4 in) | ~200 in | 17 ft |
| 12 ft (144 in) | 19 | 190 in (15 ft 10 in) | ~238 in | 20 ft |
| 14 ft (168 in) | 22 | 220 in (18 ft 4 in) | ~277 in | 24 ft |
Last updated: October 2026 · Estimates use 7.75-in rise and 10-in run. Verify your local code — most jurisdictions cap rise at 7.75 in and treads at a minimum 10 in.
Stair stringer FAQ
Measure from the top of the finished upper floor to the top of the landing surface — the full vertical drop the stairs must climb. Don't measure to the subfloor; the finished flooring changes the number.
Recalculate: divide the total rise by a whole number of steps so every step is exactly equal. A stair with one odd step is a tripping hazard and fails most inspections.
Space stringers about 16 inches apart. A 36-in-wide stair uses three stringers; a 48-in stair uses four. Never use fewer than three, even for a short step.
No — stairs longer than about 12 ft rise need a middle landing (code requirement in most areas) and are built in two sections. Keep each flight under roughly 12 ft of rise.
Yes. Add 6–12 inches of overhang for the top connection to the header and any bottom bearing detail. Buy the board 1–2 ft longer than the hypotenuse to be safe.
Related calculators & guides
How to Calculate Stair Stringer Length
Measure total rise, pick rise and run, and cut the stringer board — with code limits and common framing mistakes.
Read the guide →