Stair Calculator

Work out the number of steps, the exact riser height, the number of treads, and the total run for a staircase — from your floor-to-floor height.

How to calculate a staircase

Stairs start from the total rise — the finished floor-to-floor height. From there:

Steps (risers) = total rise ÷ target riser height (rounded), then riser height = total rise ÷ steps

The number of treads is always one less than the number of risers, because the top floor itself acts as the last "step." Total run is the number of treads times the tread depth.

Comfort and code

MeasurementTypical target
Riser height7–7.75 in (lower is easier)
Tread depth10–11 in minimum
Comfort rule2 × riser + tread ≈ 24–25 in

Good to know

  • Keep risers equal. Codes require all risers within about 3/8 in of each other — uneven steps are a trip hazard.
  • Mind the headroom and total run. A longer run needs more floor space; check it fits before you frame.
  • Confirm local code. Riser/tread limits and handrail rules vary by jurisdiction.

Frequently asked questions

How many steps for a 9 ft floor height?
108 inches ÷ 7.5 ≈ 14 steps, giving an actual riser of about 7.7 in and 13 treads.
What's the max riser height?
Usually about 7.75 in, with a minimum tread of about 10 in — but always confirm your local code.
Why is there one fewer tread than risers?
The upper floor surface serves as the final landing, so you step up one more riser than the number of treads.
What makes stairs feel comfortable?
Aim for 2 × riser + tread ≈ 24–25 in, with risers around 7–7.5 in and treads of 10–11 in.

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