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Stair Calculator

Calculate the number of steps, actual riser height, and total horizontal run for a staircase from floor-to-floor height.

Total floor-to-floor height in inches (e.g. 9 ft = 108 in)
Target riser height in inches (IRC: 4–7¾ in)
Horizontal tread depth in inches (IRC minimum: 10 in)

Results

Number of Steps14 steps
Actual Riser Height7.714 in
Total Horizontal Run11.67 ft
Stringer Length14.73 ft

📖What is it?

The Stair Calculator determines the optimal number of risers for a staircase, the precise actual riser height, the total horizontal footprint, and the stringer board length. Consistent riser heights are critical for safety — varying even ¼ inch can cause trips and falls.

🎯How to use

1. Measure and enter the total rise (floor to finished floor) in inches. 2. Enter your desired riser height (7 to 7½ inches is comfortable for most people). 3. Enter the tread depth / going (minimum 10 inches per IRC). 4. The calculator shows the optimal step count and the actual riser height that evenly divides the total rise.

💡Example scenario

A floor-to-floor height of 108 inches (9 ft) with a 7.5 in desired riser: numSteps = round(108/7.5) = 14 steps. Actual riser = 108/14 ≈ 7.71 in. Total run = 14 × 10 = 140 in = 11.67 ft.

🏆Pro tip

The "7-11 rule" is a handy comfort check: riser + tread should equal 17–18 inches (e.g. 7½ + 10 = 17½ ✓). Headroom must be at least 6 ft 8 in (IRC) measured vertically from any tread nosing to the ceiling or landing above.