How to Calculate Stair
What is Stair?
A stair calculator determines the optimal number of steps, riser height, and tread depth for a given floor-to-floor height. Building codes specify maximum riser height (7.75" in the US) and minimum tread depth (10") to ensure safe, comfortable stairs.
Step-by-Step Guide
- 1Measure total rise: the vertical distance from one floor to the next
- 2Divide by ideal riser height (~7.5") to find number of steps
- 3Round to nearest whole number and recalculate exact riser height
- 4Use Blondel formula: 2R + T = 24–25" (R=riser, T=tread) for comfort
Worked Examples
Input
Floor-to-floor height: 9 ft (108 inches)
Result
14 steps, 7.71" riser, 9.58" tread
108/14 = 7.71" riser
Input
Height: 8 ft (96 inches)
Result
13 steps, 7.38" riser, 10.24" tread
Comfortable standard stair
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