Stair Stringer & Railing Calculator with SVG Cutting Diagram
Riser, run, stringer cuts and railing counts that pass code the first time — with a to-scale cutting diagram you can take to the saw.
- IRC-code planning math with explicit pass/fail on throat depth — no shortcuts sold as expertise.
- No account, no email
- No data leaves your browser
Framing
Cut list
Railing (2 sides): 6 posts per side · 168 in rail · ≈24 balusters/side at ≤4 in gaps.
Stringer cutting diagram (to scale, one stringer)
Solid orange line = cut path. Dashed rectangle = 2x12 stock laid along the slope. Use the printed dimensions with your framing square — the on-screen graphic is proportional, not a 1:1 template.
Why first steps trip people
Code (IRC R311.7.5.1) caps risers at 7¾ in and requires every riser within 3/8 in of its neighbors. (The 6.5 in floor shown as guidance is a comfort target, not code.) Two failure modes cause almost every "first step feels wrong" complaint: (1) the total rise was measured framing-to-framing while the landing gets a finished surface later, and (2) the bottom riser wasn't shortened by the tread thickness, so the first step onto the stairs is one tread shallower than the rest. Enter the finished-floor delta and this calculator shortens the bottom cut automatically (standard-drop style).
Stringer throat — the uncut wood left under the steps, measured perpendicular to the slope — wants ≥ 3.5 in (a widely used safe-building minimum); deeper risers eat the throat, which is when you buy 2×14 stock. All angles come out of the rise/run triangle: 37.3° here, which also sets your speed-square pivot for laying out the teeth.
What people hate about the other tools
We read the reviews of the incumbents before writing this page. Every complaint below maps to a decision in the tool above.
Built the stairs framing-to-framing, then the pavers went in and the bottom step is 5 inches while the rest are 7
In this toolA dedicated finished-floor input adjusts total rise before the first cut is laid out.
One-line difference: Finished-floor rise input and automatic tread-drop on the bottom riser — the two omissions behind nearly every 'first step trips me' staircase — plus a printable to-scale cutting diagram.
Free forever, Pro when you need the paperwork
Free no signup, no card
- Code-window riser fitting (6.5-7.75 in) with variance warnings
- First-riser cut shortened by tread thickness (drop style)
- Throat-depth pass/fail and stock size recommendation
Pro $7 once
- Full-size printable cutting template PDF per stringer
- Landing platform & 90° turn configurations
- Material shopping list across stringers, treads, railings & fasteners
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