Stairs Calculator

in
Measure from finished floor to finished floor.
in
IRC max: 7-3/4 in (7.75). Ideal: 7–7.5 in.
Construction

Calculate the number of steps, riser height, and tread depth for a staircase.

Formula

Steps = round(total rise / riser); Tread ≈ 17.9 − riser
  • IRC building code: max riser 7-3/4 in; min tread 10 in; max riser variation 3/8 in.
  • Comfort formula: riser + tread ≈ 17.5–18 in.
  • Stringer length = √(total run² + total rise²).

9 ft floor-to-floor (108 in), 7 in risers

Inputs
  • Total Rise (floor to floor): 108 in
  • Desired Riser Height: 7 in

108 ÷ 7 ≈ 15 steps. Actual riser = 108/15 = 7.2 in. Tread = 17.9 − 7.2 = 10.7 in.

Frequently asked questions

What is the code for stair rise and run?
IRC: max rise 7-3/4 in, min run 10 in. Consistent rise throughout is critical.