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Stair Calculator

Rise, run and stringer length that meet code.

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Code check

Other step counts

The rise must divide evenly, so the step count is what you adjust.

RisersRise eachTotal runMeets code

Rise per step

—

Layout

Number of treads—
Total run—
Stringer length—
Stair angle—

Checks

Rise + run rule—
Walking line—

—

Against common residential code limits

Residential codes commonly cap the riser at 7¾ inches and require a tread of at least 10 inches, with variation across a flight limited to about 3/8 of an inch. These are typical values — your local code takes precedence, and stairs are one of the most heavily inspected parts of a build.

Quick Tool Overview

The Stair Calculator lays out a staircase from the total floor-to-floor rise, finding step counts that divide it evenly and reporting riser height, tread depth, total run, stringer length and angle — each checked against building code limits.

What it does
Calculates a complete stair layout from the total rise
You give it
Total rise, a step count and a tread depth
You get back
Riser height, run, stringer length, angle and code check
Best for
Deck stairs, basement stairs and renovation planning
Calculators Free, unlimited use No sign-up Runs in your browser

About the Stair Calculator

Lay out a staircase from a single measurement — the total rise from finished floor to finished floor. The calculator finds a step count that divides that height evenly, then reports the rise per step, tread depth, stringer length, total run and the angle.

Every result is checked against the dimensional limits building codes set, because stairs are one of the most heavily regulated parts of a house and for a good reason: uneven risers are a genuine trip hazard, since people climb stairs by rhythm rather than by looking. The largest and smallest riser in a flight typically must not differ by more than about 3/8 of an inch, which is why the step count must divide the total rise evenly rather than approximately.

Key features of the Stair Calculator

Code limits checked

Riser height and tread depth are compared against the common residential maximums, with a pass or fail on each.

Even risers enforced

Step counts are chosen so the rise divides evenly, because an inconsistent riser is a real trip hazard.

Several counts compared

A table of candidate step counts with the riser height each produces, so you can pick the best fit.

Stringer length calculated

The hypotenuse of rise and run, which is what you actually buy timber for.

Angle and headroom

The stair angle and the headroom clearance, both of which codes also constrain.

How to use the Stair Calculator

  1. 1

    Measure the total rise

    Finished floor to finished floor, not floor to joist. This is the measurement everything else derives from.

  2. 2

    Choose a step count

    Suggested counts are listed with the riser height each produces, and whether it meets code.

  3. 3

    Set the tread depth

    Typically 10 to 11 inches. Deeper treads make a longer, shallower flight.

  4. 4

    Read the layout

    Riser height, total run, stringer length, angle and headroom, all code-checked.

Frequently asked questions

Residential codes commonly cap the riser at 7¾ inches (about 196 mm) and require a minimum tread depth of 10 inches. Commercial limits are stricter. Always confirm against your local code.

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