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✓ IRC 2024 Section R311.7 Code

Stair Stringer Calculator

Calculate precise step count, riser height, run length, stringer diagonal cuts, and incline angle.

Staircase Rise & Tread Settings

Finished floor to finished floor
IRC minimum is 10.0"
Stringer Layout Specifications
Exact Step Count 10 Steps
Riser Height 7.50"
Total Horizontal Run: 99.0" (8.25 ft)
Stringer Cut Length: 124.2" (10.35 ft)
Incline Angle: 37.1° (Optimal)
IRC R311.7 Compliance: Compliant
Riser Variation (max 3/8"): Uniform by calculation ✓

Frequently Asked Questions

What is the standard residential stair code (IRC 7/11 Rule)?

According to the International Residential Code (IRC), the maximum riser height is 7.75 inches (approx. 7 3/4"), and the minimum tread depth is 10.0 inches. The difference between the highest and lowest riser in any flight of stairs must not exceed 3/8 inch.

How do you calculate the number of steps needed?

Measure the exact total vertical rise from the lower finished floor to the upper finished floor (in inches). Divide the total rise by 7.5 (the ideal riser height). Round to the nearest whole number to get the total number of risers. Then divide the total rise by that number to get the exact height of each riser.

What is the ideal angle for a residential staircase?

The optimal and most comfortable incline angle for indoor residential stairs is between 30° and 37°. Angles above 42° feel like a steep ladder, while angles below 25° feel like a ramp.