Stair Calculator - Professional Staircase Design & Building Tool

This professional stair calculator is designed to help homeowners, contractors, and builders calculate accurate stair dimensions that comply with the International Residential Code (IRC). Whether you're planning interior stairs, exterior deck stairs, or basement access, our tool provides precise measurements for riser height, tread depth, stringer length, and material requirements.

The calculator automatically checks IRC building code compliance, including riser height limits (4-7.75 inches), minimum tread depth (10 inches), stair width requirements (36 inches minimum), and headroom clearance (80 inches minimum). It also validates the 2R + T rule for comfortable stairs and provides warnings for optimal stair angles (30-40 degrees).

For material estimation, the calculator determines the exact number of treads, risers, and stringers needed, along with total lumber in board feet. The cost estimation feature helps you budget for materials, labor, and handrails. All calculations are based on industry-standard formulas and building codes used by professional contractors.

The International Residential Code (IRC) establishes minimum safety standards for residential stair construction. These codes ensure stairs are safe, comfortable, and accessible. Key requirements include consistent riser heights (maximum 3/8 inch variation), adequate tread depth for foot placement, sufficient width for passage, and proper headroom clearance.

Handrails are mandatory for stairs with 4 or more risers and must be positioned 34-38 inches above the stair nosing. For stairs wider than 44 inches, handrails are required on both sides. Landings are required every 12 feet of vertical rise and must be at least 36 inches deep. Always check your local building codes, as they may have additional requirements beyond IRC standards.