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Stair calculator

Enter the floor-to-floor rise to estimate a straight flight. The upper landing counts as the final walking surface.

Measure your flight

The upper landing is the final walking surface.

Floor to floor. Required; above 0, up to 240 in.

Visible default: 7.75 in. Sets the highest desired riser.

Visible default: 10 in. Depth of each constructed tread.

Changing the check mode keeps your measurements.

Your measurements stay in this page. Nothing is saved or sent.

Your stair geometry

Enter the total floor-to-floor rise, check the visible defaults, then calculate.

Results include riser and tread counts, actual rise, horizontal run and a proportional side view.

Application bounds: total rise above 0–240 in; maximum riser 0.25–24 in; tread depth above 0–60 in; up to 128 risers. These are tool limits.

Headroom, landing design, handrails, nosings, construction tolerances, loads, end cuts, local adoption and amendments are not evaluated. No structural plan, cut list or concrete-volume estimate is provided.

Reference: ICC-hosted 2021 IRC Plan Review training PDF, pp. 24–25, accessed October 11, 2026. The direct code-section page was inaccessible; this reference does not verify locally adopted code.

How the count works

Divide total rise by the maximum riser and round the count up. Actual riser height is total rise divided by that whole count. A flight with N risers has N−1 constructed treads because the upper landing provides the last walking surface.

Horizontal run is constructed treads × tread depth. The diagonal uses the rise and run; it is a geometric slope estimate, not a finished stringer cut length.

Worked example: 108 inches

With 108 in of rise, a maximum riser of 7.75 in and 10 in treads, ceil(108 ÷ 7.75) gives 14 risers. There are 13 constructed treads, actual rise is 54/7 in (about 7.714 in), and horizontal run is 130 in. The slope estimate is √28564, about 169.009 in.

Dimensional reference and limits

The 2021 IRC dimensional reference checks actual riser ≤7.75 in, tread depth ≥10 in when a tread exists, and single-flight rise ≤151 in. The source is ICC-hosted plan-review training material, pages 24–25, reviewed October 11, 2026. Local adoption and amendments are not verified.

This calculator does not check headroom, landings, rails, nosings, loads, structural design or cut details. User-entered dimensions are unverified. Ask your local building authority about the rules that apply.

Sources

Frequently asked questions

Why is the maximum riser different from the result?

The maximum sets an upper limit. Rounding the riser count up usually makes each actual riser a little shorter.

Why one fewer tread than risers?

The count treats the upper landing as the final walking surface. One riser therefore has zero constructed treads and zero horizontal run.

Does switching units change the flight?

The tool retains exact dimensions while displaying inches or centimeters. Editing a displayed value replaces that dimension.

Can I use the diagonal as a stringer cut length?

No. End cuts, support, nosings and construction details need a separate design. Concrete volume and structural stringer calculations are outside this tool.