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Stair Calculator

Calculate riser count, actual riser height, total run, and geometric stringer length from total rise, target riser height, and tread depth.

Content updated October 7, 2026 · Details

Published

Content updated

Recorded calculation check · Verification scope

Number of steps

Inputs ↓
Number of risers
14
Actual riser height
7.71 in
Entered tread depth
10.00 in
Total run needed
130.00 in
Stringer length
169.01 in

Geometry worksheet using the entered target riser and tread depth. It does not establish code compliance or field fit.

in
in
in

Results update as you type.

Result links include your inputs in the URL. Anyone with the link can read them; avoid sharing sensitive values.

Compare scenarios

Save a result, change your inputs, then compare. Up to three saved scenarios for this visit.

Worked example

totalRise: 108 · targetRiser: 7.5 · treadDepth: 10

Result: 14

Try it →

Calculate riser count, actual riser height, total run, and geometric stringer length from total rise, target riser height, and tread depth.

Inputs and method

Enter total rise, target riser height, and tread depth. Riser count is the nearest positive whole count to total rise ÷ target rise; actual rise, total run for one fewer tread, and diagonal stringer length follow from that geometry.

Calculations retain full floating-point precision until the labeled display step. Counts and packages use an explicit upward ceiling only where a whole purchase unit is required.

Interpreting the estimate

Use the result as a planning value and keep input precision consistent with the measurements or source data you have. Small displayed differences can come from final-place rounding; intermediate values are not rounded.

Assumptions and limits

Target dimensions are user inputs, not recommendations. The worksheet does not establish code compliance, headroom, landings, nosing, structure, or field fit. For deck stairs and stringers as part of a deck takeoff, use the deck material calculator; for concrete stair geometry, see the concrete calculator; and for the same rise-and-run conversion on a roof, use the roof pitch calculator.

Empty entries, invalid numbers, prohibited negatives, zero denominators, impossible relationships, and unsupported options trigger a validation message instead of a misleading result.

Compare a geometry option before a specification check

Keep the measured total rise fixed while testing another target riser height, then examine the resulting geometry with the entered tread depth. Save those assumptions with the output. Before construction, the actual layout, materials, and applicable requirements need their own check; the modeled geometry does not certify a compliant stair.

Sources

Compare Stair Calculator with related tools

All comparisons →
Ladder Safety vs Stair CalculatorCompare ladder safety and stair calculators: one plans an extension-ladder setup with the 4 to 1 rule, the other breaks a rise into stair steps — and which access job each fits.Stair vs Concrete CalculatorCompare the stair calculator and the concrete calculator: one settles step geometry and stringer length, the other turns the pour into cubic yards, bags, and dry-mix weight.Stair vs Roof Pitch CalculatorCompare stair and roof pitch calculators: both work with rise and run, but one sizes stair steps and stringers while the other converts roof slope among pitch ratio, percentage, and angle.

Frequently asked questions

How does the calculator determine the number of risers?

It divides total rise by your target riser height and takes the nearest positive whole count. Actual rise, total run for one fewer tread, and diagonal stringer length are then derived from that count.

Does the result mean the stairs are code compliant?

No. Target dimensions are inputs, not recommendations, and the worksheet does not establish code compliance, headroom, landings, nosing, structure, or field fit. Qualified trades and adopted codes control safety-critical work.

When does the form show a validation message?

Empty entries, invalid numbers, prohibited negatives, zero denominators, impossible relationships, and unsupported options trigger a validation message instead of a misleading result.

Sources

  • 2024 International Residential Code

    primary · Aug 12, 2026

    Supports: The 2024 International Residential Code stair provisions are the adopted-code context the page references for riser height, tread depth, and compliance boundaries.

    — v2024 edition

  • Walking-working surfaces stairways

    primary · Aug 12, 2026

    Supports: OSHA 29 CFR 1910.25 sets stairway riser-height and tread-depth requirements that support the page's warning that qualified trades and adopted codes control safety-critical work.

  • Guide to Stairways

    primary · Aug 12, 2026

    Supports: The Access Board's ADA stairways guide supplies the uniform-step and geometry context the page relies on for its rise-and-run planning discussion.

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Stair Calculator updated at

Recorded calculation check

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