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The Locolory toolkit / Carpentry & Framing

Stair Rise, Run & Stringer Calculator

Calculate riser count, step height, tread depth, stringer length, and incline angle with an IRC model-code dimensional check.

What is the standard rise and run for residential stairs? The 2021 IRC model code limits typical residential stair risers to 7¾ inches maximum and requires 10 inches minimum tread depth; a roughly 7-inch rise and 11-inch run is a common comfort target, not a standalone code rule.

  • Key formula: Riser Count = Total Rise ÷ Target Rise, rounded to a whole number; Exact Rise = Total Rise ÷ Riser Count.

Visualized on a local client-side SVG canvas.

● Calculated 100% locally in browser

Stair geometry + stringer profile

Risers

14

Exact rise

7.714"

Treads

13

Total run

136.50"

Stringer

174.06"

Incline

36.3°

Passes selected IRC dimensional limits · local approval required
Rise 7.71 · tread 10.50 · diagram scaled

The 7–11 Rule & IRC Stair Code Requirements

The 7–11 rule is a comfort shorthand. Model-code dimensional checks still govern maximum riser, minimum tread, landings, width, headroom, guards, and handrails.

The 2021 IRC limits risers to 7¾ inches and variation within a flight to ⅜ inch. Tread depth is generally at least 10 inches. Confirm the code edition and amendments adopted by your jurisdiction.

This tool assumes uniform geometry and does not verify headroom, nosing, structural capacity, landings, or field conditions.

Stair Angle & Lumber Sizing Reference

Residential stairs commonly fall near 30°–37°. The comfort value 2 × rise + run often lands near 24–25 inches, but neither range replaces code review.

2×12 stringers are common because notches leave more material than narrower stock. Actual capacity depends on remaining throat, lumber properties, span, spacing, support, and loads.

Measure finished floor to finished floor and account for finished tread thickness before cutting.

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Good questions. Clear answers.

How do you find the exact number of steps for a given height?

Divide total finished-floor rise by a target riser height, round to a practical whole number of risers, then divide the total rise by that count. Verify the resulting exact riser against the locally adopted code.

Why is the bottom stair riser cut shorter than the other risers on a stringer?

When tread material sits on top of a cut stringer, the bottom plumb cut is commonly reduced by the tread thickness so the finished first rise matches the other finished risers.

What is the maximum allowed variation between stair step heights?

The 2021 IRC model code limits the difference between the greatest and smallest riser in one flight to 3/8 inch. Local amendments and project conditions may differ.

What size lumber is required for cutting stair stringers?

2×12 lumber is common, but required size, species, grade, remaining throat, span, spacing, and support depend on design loads and local code. Have the framing design reviewed where required.