How many steps do I need?

Divide the total rise (floor-to-floor height) by your target step rise, around 7 inches, and round to the nearest whole number. That gives the number of risers; the number of treads is one fewer.

What is a comfortable stair rise and run?

A common rule is a rise of about 7 inches and a run (tread depth) of about 11 inches. Many codes cap the rise at 7.75 inches and require a run of at least 10 inches. A good check is that 2 × rise + run falls between about 24 and 25 inches.

How long does a stair stringer need to be?

The stringer length is the diagonal of the staircase, found with the Pythagorean theorem: the square root of (total rise squared plus total run squared). This calculator works it out for you.

Stair Calculator — Rise, Run & Number of Steps

Staircase

Units

Total rise in The vertical height from the lower floor to the upper floor (finished surfaces).

Target step rise in Around 7 in (18 cm) is comfortable. The tool picks the step count closest to this.

Tread depth (run) in The horizontal depth of each step, not counting nosing overhang.

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How to calculate a staircase

Stairs are all about dividing your total rise — the floor-to-floor height — into equal steps that are comfortable and safe to climb. You pick a target step height (rise), the calculator finds the whole number of steps that gets closest to it, then works out the exact rise per step, the total run, and the diagonal stringer length you'll cut.

The formula, step by step

1. Number of risers = total rise ÷ target rise, rounded to a whole number.
2. Actual rise per step = total rise ÷ number of risers.
3. Treads = risers − 1 (the top landing is the last "step").
4. Total run = treads × run. Stringer = √(rise² + run²).

Comfortable, code-friendly proportions

Most U.S. residential codes (IRC) allow a maximum rise of 7¾ in and require a minimum run of 10 in. A long-standing comfort rule is that 2 × rise + run ≈ 24–25 in. This calculator flags your design if the rise or the rise-plus-run check falls outside the usual safe range — but always confirm against your local code.

Rise & run quick reference

Measure	Comfortable	Typical code limit
Step rise	~7 in	≤ 7.75 in
Tread run	~11 in	≥ 10 in
2 × rise + run	24–25 in	—

A note on safety

Every step in a flight should be the same height — uneven steps are a major trip hazard and usually a code violation. This calculator keeps all steps equal by design. For structural stringers, handrails, and landings, follow your local building code and, for anything load-bearing, have the design checked.