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Straight stair calculator

Enter total rise and available run. Get riser, tread, stringer length and angle, a live code check, and a complete build packet PDF.

Straight Stair
in
in
in
in
✎
Elevation — side view—
Results ↓ Download full PDF
Steps
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Riser
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Tread
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Stringer
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Angle
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2R+T
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How the straight stair calculation works

The step count is the total rise divided by your target riser height, rounded to the nearest whole step. Dividing total rise by that step count gives the actual riser height, kept equal across every step as code requires. Tread depth is the available run divided by the number of treads, which is one less than the step count because the top step lands on the floor above.

stringer length = √(total rise² + total run²)
angle = atan(total rise / total run)
comfort (Blondel) = 2 × riser + tread ≈ 24–25 in
Compliance thresholds shown here are being finalized against primary code sources. Always confirm against the building code edition enforced by your local authority having jurisdiction before cutting or pouring.

Reading the code check

Pick your jurisdiction in the calculator header. Each result re-checks live against that code's riser, tread and width limits, with the governing clause shown beside every line. Switching between editions — IRC 2021 and 2024, for example — recalculates instantly.