Build · Deck
Plan risers, treads, and stringer length with Standard or Flush mount. IRC-style starting points.
Defaults follow IRC-style R311.7.5 limits commonly reprinted by building departments (max riser 7¾ in, tread ≥ 10 in). Your AHJ may amend these.
Need a dedicated stringer URL with IRC table? Stair stringer calculator
Scenario templates
Calc mode
Stringer mount
Standard mount: stringer drops below deck so the first tread is one riser down — treads = risers − 1.
Tread type (affects depth hint)
Common PT board depth planning
Layout summary
8
risers
7.5 in
actual riser (≤ 7¾ in target)
7
treads (risers − 1)
Interactive 3D stair (8 risers · 7 treads)
Drag to orbitUpdates when riser count, riser height, or tread depth change. Planning visual only — not a cut list or engineered stringer.
Based on commonly adopted IRC R311.7.5 language (max riser 7¾ in, min tread 10 in, uniformity within ⅜ in) as reprinted by municipal handouts. Local amendments, landings, handrails, guards, and nosings are separate — confirm with your building department before cutting stringers.
Number of risers, actual riser height, tread count (Standard: risers − 1; Flush: = risers), stringer run, tip-to-tip planning length, stair angle, and mount compare. 3D model mirrors riser/tread counts.
Does not replace
Supply yard
Starting points for planning — not a site-specific design. Footnotes point to sources on this page.
| Topic | Typical starting value | Source notes |
|---|---|---|
| Maximum riser height | 7¾ inches (196 mm) | IRC R311.7.5.1 as reprinted by Placer County & City of Boise handouts (verify adopted edition). |
| Minimum tread depth | 10 inches (254 mm) | IRC R311.7.5.2 municipal reprints above. |
| Uniformity | Largest vs smallest riser or tread within a flight ≤ ⅜ in | Same IRC R311.7.5.1 / R311.7.5.2 language in municipal PDFs. |
| Open risers (when used) | Openings more than 30 in above grade: no 4 in sphere passage | IRC R311.7.5.1 open-riser provision in the same handouts. |
| Local overrides | AHJ / state amendments can differ | Always check the code edition your city adopted. |
Short DIY narratives. Numbers match the one-click scenario presets in the calculator (US units).
DIY deck threads often ask for a “stair stringer calculator.” Measure total rise from finished deck to finished grade/landing, set max riser and tread depth, then use the tip-to-tip planning length before you cut pressure-treated stringer stock. This page covers that geometry; engineered stringer sizing and connections still need code-compliant details.
The tool picks the smallest riser count that stays within your max, then divides rise evenly. We cite municipal IRC reprints (Placer County, City of Boise) and point to ICC Digital Codes for the primary section. We do not invent section numbers beyond what those sources support.
Risers = ceil(total rise ÷ max riser). Actual riser = total ÷ risers. Treads = risers − 1. Stringer run ≈ treads × tread depth. Length ≈ √(run² + total rise²).
Yes for planning geometry. It sizes riser count, actual riser height, tread count, stringer run, and tip-to-tip planning length from total rise — the numbers you need before cutting a stringer. It does not engineer stringer depth, connections, handrails, or guards.
After the tool divides total rise into equal risers, stringer run ≈ treads × tread depth, and planning length ≈ √(run² + total rise²). Buy stock longer than that tip-to-tip length and verify layout with your AHJ.
Defaults follow commonly adopted IRC R311.7.5 limits as reprinted by U.S. building departments: max riser 7¾ in, min tread 10 in, with uniformity within ⅜ in. Always confirm the edition your city adopted.
No. The interactive stairs mirror your riser/tread counts for visualization only. Permits, inspections, and engineered connections stay with your AHJ and licensed pros when required.
We cite extension services, manufacturer guidance, and municipal/IRC reprints. This is not legal advice, not a substitute for a licensed engineer or architect, and not approval from your Authority Having Jurisdiction (AHJ). Adopted codes and product warranties vary by place and year — verify before you buy or cut.
Municipal reprint of IRC-style R311.7.5: max riser 7¾ in, min tread 10 in, uniformity ≤ ⅜ in. Local California amendments may apply; always confirm with your AHJ.
Building-department handout aligning with IRC R311.7.5 riser/tread limits.
Primary IRC digital codes entry for stairways. Full text may require ICC account; use with municipal handouts above.
Full site bibliography: Sources hub.
Yards, tons, density table, overage vs compaction, optional cost.
Buy-depth after existing, bags↔bulk ledger, multi-bed, coverage table.
X/12, degrees, % slope, rafter teaser, pitch compare.
Line length & angle — not IRC span-table design.
Stringer length + IRC R311.7 table on one screen.
