Standard Stair Width and Other Important Measurements

The standard stair width for residential stairs in the U.S. is 36 inches minimum, according to building codes. Many homeowners choose widths between 36 and 42 inches for comfort. Wider stairs, up to 48 inches, are also common in modern homes to allow easier passage and moving of large items.

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MeasurementStandard / Code Requirement
Stair width36 inches minimum; 36–42 inches typical
Tread depth (run)Minimum 10 inches
Riser heightMaximum 7 3/4 inches
Tread thickness1 to 1 1/4 inches
HeadroomMinimum 6 feet 8 inches
Landing widthEqual to stair width; minimum 36 inches
Open riser spacingLess than 4 inches
Nosing projection3/4 inch to 1 1/4 inches

Spiral Staircases

For spiral staircases, the IRC recommends a minimum diameter of 5 feet. Each tread should provide a walking width of at least 36 inches.

Railing Guidelines

  • Railing height: 34–38 inches
  • Spindle spacing: No more than 4 inches apart
  • 27-inch rule: If handrails are on both sides, there must be at least 27 inches of clear width between them.