Free Stair Stringer Calculator — Length, Count & Layout (2026)

How to Use This Calculator

1. 1Enter the total rise (vertical height) of the staircase in inches.
2. 2Enter the run per step (horizontal tread depth) — 10 inches minimum per IRC.
3. 3Enter the total number of steps (use the Stair Calculator to determine this).
4. 4Enter the stair width to calculate the number of stringers needed.

About This Material

Stair stringers are the backbone of any staircase, carrying the weight of the treads, risers, and everyone using the stairs. Standard stringers are cut from 2x12 dimensional lumber, which provides enough material for the notch cuts while maintaining the required 3.5 inches of uncut wood below each notch for structural strength. For exterior applications, use pressure-treated #1 or better 2x12 Southern Yellow Pine or Douglas Fir. For interior stairs, kiln-dried SPF (Spruce-Pine-Fir) or Douglas Fir 2x12 is standard. Never use 2x10 lumber for cut stringers — after notching, there is not enough structural material remaining. Closed (uncut) stringers use a housed design with routed dadoes and can be made from 2x10 or engineered lumber. Metal stringer brackets (Simpson LS) eliminate the need for notch-cutting and can be stronger than traditional cut stringers. Pre-made steel stair stringers are also available for deck and exterior applications at $40 to $80 per stringer. A standard 2x12x16 board for stringers costs $20 to $45 depending on species and grade. Budget $100 to $250 per staircase for stringer lumber alone.

Installation Tips

• •Use a framing square with stair gauges clamped to the rise and run dimensions for repeatable cuts.
• •Make all cuts with a circular saw and finish corners with a handsaw — do not overcut with the circular saw.
• •Test-fit the first stringer before cutting the rest — verify it sits flush against the header and floor.
• •Use metal stringer hangers (Simpson LSC) at the top connection for a secure, code-compliant attachment.
• •Sand all cut edges on exterior stringers and apply end-cut preservative to prevent moisture wicking.

Common Mistakes to Avoid

• ⚠Overcutting stringer notches with a circular saw — this weakens the stringer at the corners. Finish with a handsaw.
• ⚠Using 2x10 instead of 2x12 — after notching, the remaining wood depth will be less than the required 3.5 inches.
• ⚠Not dropping the bottom riser by one tread thickness — the first step will be taller than the rest.
• ⚠Spacing stringers too far apart — maximum 24 inches on center, 16 inches recommended for wider stairs.

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