Stair Calculator
Calculate stair riser height, tread depth, and stringer length. Automatically checks IRC building code compliance for safe stair construction.
Vertical distance from floor to floor
Horizontal distance. Required for tread depth and stringer length.
About the Stair Calculator
Building safe stairs requires precise calculations. The total rise is the vertical distance between floor levels (measured in inches), and the total run is the horizontal distance the staircase covers. The riser height is the vertical face of each step, and the tread is the horizontal surface you step on. The stringer is the diagonal board that supports the treads, and its length is calculated using the Pythagorean theorem: √(rise² + run²). For planning your project's material needs, the Concrete Calculator can help estimate concrete for landings and footings.
IRC (International Residential Code) standards require risers to be between 4 and 7.75 inches tall, and treads to be at least 10 inches deep. All risers within a single staircase must be within 3/8 inch of each other for safety. The ideal riser height is commonly cited as 7 inches and the ideal tread depth as 11 inches — though specific local codes may vary. If you're planning a complete home renovation, use the Square Footage Calculator to measure floor areas before estimating material quantities.
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For a related calculation, use Roofing Calculator to calculate roof area, squares, and bundles of shingles needed based on footprint and roof pitch. Alternatively, use Square Footage Calculator to calculate square footage for rectangles, triangles, circles, and trapezoids. Estimate material costs.