Stair Calculator
Number of steps, rise, and run for a staircase to a given height.
Input sheet
DIY at your own risk. Calcora's calculators and guides are general estimates and information only — not professional, engineering, legal, or safety advice. Always verify local building codes and permit requirements, and hire a licensed pro for electrical, gas, plumbing, structural, or any work you're not fully comfortable doing yourself.
Comfortable, code-compliant stairs come down to two numbers — the riser height and the tread depth — and getting them right is what makes a staircase feel safe instead of treacherous. This calculator works them out from your total rise.
How it works
Total rise divided by an ideal ~7 in riser gives the step count; exact riser height is rise divided by steps. Run is treads times step count minus one.
The calculator divides total rise by an ideal riser of about 7 inches to get a whole step count, then divides the rise back by that count to find the exact riser height. Total run is the tread depth times the number of treads, which is one less than the number of risers.
The relationship between rise and run is what makes stairs feel natural. Risers near 7 inches with treads around 10–11 inches match the human stride; stray too far and people stumble.
Steps = total rise ÷ 7, rounded to nearest whole; riser height = total rise ÷ steps; total run = (steps − 1) × tread depth.
Worked examples
A total rise of 108 inches (a standard 9-foot floor) with 10-inch treads. → 15 steps, 7.2-inch risers, 140-inch run.
108 ÷ 7 ≈ 15.4, rounded to 15 steps. Riser = 108 ÷ 15 = 7.2 in. Run = (15 − 1) × 10 = 140 in.
A 48-inch rise to a deck with 11-inch treads. → 7 steps, about 6.86-inch risers, 66-inch run.
48 ÷ 7 ≈ 6.9, rounded to 7 steps. Riser = 48 ÷ 7 ≈ 6.86 in. Run = (7 − 1) × 11 = 66 in.
Tips & gotchas
- Keep every riser within about 3/8 inch of the others — uneven risers are a trip hazard and a common code violation.
- Check your local building code for maximum riser and minimum tread limits before you cut stringers; they vary by jurisdiction.
- A comfortable stair satisfies the old rule of thumb: two risers plus one tread should land around 25 inches.
- Confirm you have enough horizontal run and headroom for the total run the calculator gives before committing the layout.
FAQ
What's a comfortable riser height?
Around 7 to 7.75 inches. Lower than 6 inches feels like an awkward shuffle, and over 8 inches is a strain to climb. The calculator targets the comfortable 7-inch range.
Why must all risers be the same height?
People learn the rhythm of a staircase within the first step. A single odd riser breaks that rhythm and causes falls, which is why codes tightly limit the variation between risers.
How much horizontal space will my stairs take?
The total run the calculator gives — tread depth times the number of treads. Make sure your floor plan has that length plus landing space before settling the design.
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