What is the ideal stair rise and run?

Building codes typically require 7-7.75 inch rise (max) and 10-11 inch run (min). The comfort formula 2R + T = 24-25 inches ensures comfortable climbing. For example: 7" rise + 11" tread = 25" (ideal).

How do I calculate the number of steps?

Divide total rise (floor-to-floor height) by desired rise per step. For 9-foot ceiling (108 inches): 108 ÷ 7.5 = 14.4, round to 14 steps. Then recalculate: 108 ÷ 14 = 7.71 inches per step.

What is stair headroom and why is it important?

Headroom is the vertical clearance from the nosing to any obstruction above. Minimum is 6'8" (80 inches). Insufficient headroom is a code violation and safety hazard. Consider headroom when planning stair openings.

How do I calculate stringer length?

Use the Pythagorean theorem: length = √(total rise² + total run²). For a stair with 9 ft rise and 12 ft run: √(81 + 144) = √225 = 15 feet stringer length. Add extra for top and bottom cuts.

What are common stair building code requirements?

IRC/IBC codes require: max 7.75" rise, min 10" tread depth, min 36" width, max 12 risers between landings, 6'8" min headroom, and handrails on one side. Local codes may be stricter.

How wide should stairs be?

Residential stairs minimum 36 inches, commercial 44 inches. Main stairs in homes are often 42-48 inches for comfort. Measure clear width between handrails or walls, not including the handrails themselves.

Stair Calculator

IRC/IBCConstructionCode Compliance

IRC/IBCConstruction

Stair Calculator

Enter dimensions to calculate stair rise, run, and check building code compliance

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Stair Calculator

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Frequently Asked Questions

Stair Calculator

Calculation Mode

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Frequently Asked Questions

01What is the ideal stair rise and run?

02How do I calculate the number of steps?

03What is stair headroom and why is it important?

04How do I calculate stringer length?

05What are common stair building code requirements?

06How wide should stairs be?