Stair Calculator
Number of steps, riser height, tread, total run, stringer length and angle for a staircase.
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About the Stair Calculator
Plan a comfortable staircase. Enter the floor-to-floor height and your preferred riser and tread sizes to get the number of steps, the exact riser height, how much floor space the stairs take, the stringer length and the angle.
The comfort check uses the classic rule that two risers plus one tread should be about 24–25 inches (61–64 cm).
How to use the Stair Calculator
- Choose inches or centimetres.
- Enter the total height from finished floor to finished floor.
- Adjust the preferred riser height and tread depth if needed.
- Click Calculate stairs.
Formula
Risers = total height ÷ preferred riser, rounded to the nearest whole number; exact riser = height ÷ risers. Treads = risers − 1. Total run = treads × tread depth. Stringer = √(height² + run²). Angle = arctan(height ÷ run).
Examples
- 10 ft (120 in) floor to floor, 7 in risers, 10 in treads → 17 risers of 7 in, 16 treads, run 160 in (13.3 ft), angle about 37° — comfortable (2 × 7 + 10 = 24 in).
Frequently asked questions
How accurate is this?
It is a planning estimate using standard formulas. Real results depend on the equipment, installation and conditions, so confirm with a qualified installer before buying.