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Structural

Stair Calculator USA 2026

Calculate risers, treads and stringer length for a straight stair run — code-compliant to IRC 7.75" max rise / 10" min tread.

Reviewed by BuildMate Editorial Team Construction Researchers Updated March 2026 2 min read Fact-checked

Used by

250,000+ homeowners

Avg. time

~15 seconds

Updated

2026

Accuracy

Pro estimation

Works on: Desktop Tablet Mobile No registration required
Unit system

Enter your measurements

Results

Risers

15

7.20" each

Treads

14

10" each

Total run

140"

11.7 ft

Stringer length

176.8"

14.7 ft

Calculation steps
  1. 1.Risers = ⌈108 ÷ 7.5⌉ = 15
  2. 2.Rise per step = 108 ÷ 15 = 7.20"
  3. 3.Treads = 15 − 1 = 14
  4. 4.Total run = 14 × 10" = 140"

Includes a standard waste allowance. Verify with your supplier before ordering.

Stored on this device — no account needed.

What this calculator does

Estimates structural materials — beams, joists, headers, framing lumber — with span and load rules of thumb baked in.

When to use it

  • Framing a wall, floor or roof.
  • Sizing a header for a new door or window.
  • Planning a load-bearing wall removal.

Common mistakes

  • Undersizing beams for the span and tributary load.
  • Cutting engineered lumber (LVL, TJI) without manufacturer approval.
  • Skipping the structural engineer for load-bearing changes.

Pro tips

  • Always verify span tables with local code.
  • Get a stamped engineer's letter for any load-bearing removal.
  • Use LVL headers over 6' openings for reliable performance.
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Disclaimer: Estimates based on 2026 RSMeans USA data. Actual quantities vary by site conditions, waste and installer practices. Verify with your supplier or contractor before ordering.

How it works

  1. 1Enter total rise (floor to floor, in inches).
  2. 2We target 7.5" per riser and 10" tread.
  3. 3Stringer length uses Pythagorean theorem.

Formula

Risers = ⌈ Total Rise ÷ 7.5 ⌉ → Rise per step = Rise ÷ Risers

Worked example

108" rise ÷ 7.5 = 14.4 → 15 risers × 7.2" each; 14 treads × 10" = 140" run.

Frequently asked questions

Max rise per code?

IRC 2021: 7.75" max riser, 10" min tread.

How wide should stairs be?

36" minimum, 42" preferred for comfort.

Is the Stair Calculator free to use?

Yes — every BuildMate calculator is 100% free, requires no signup and works offline once the page has loaded.

How accurate are these estimates?

Formulas follow 2026 industry standards (RSMeans, ICC and manufacturer specs). Real-world results vary by site conditions, waste and installer practices — always get 2–3 written quotes from licensed pros before committing.

Can I save my calculation?

Yes. Hit the Save button after you run an estimate — it's stored on this device (no account needed) and you can access it anytime from the Saved drawer.

Can I compare two projects side-by-side?

Yes. Add estimates to Compare and open the Compare drawer to see them side-by-side, then use Download PDF or Email to share the comparison.

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