Stair Calculator
Calculate the number of steps, riser height, and total run for a staircase, in metric or imperial.
Estimates for planning only — verify riser height and going against local building codes and a qualified structural professional before construction.
How it works
- 1Enter the total rise (floor-to-floor height), your target riser height, and the going (tread depth).
- 2The calculator rounds to the nearest whole number of risers so every step is equal, then recomputes the actual riser height.
- 3Read off the step count, exact riser, tread count (risers − 1), and total horizontal run.
Use cases
- Planning a new staircase inside a home and checking it fits the available floor space.
- Verifying that a proposed riser meets the 2×riser + going ≈ 63 cm comfort rule.
- Estimating stringer length for an external deck or garden stair.
Frequently asked questions
How is the number of risers calculated?
Risers = round(total rise ÷ target riser). A 3 m rise with an 18 cm target gives round(300 ÷ 18) = 17 risers, so the actual riser is 300 ÷ 17 ≈ 17.65 cm and every step is identical.
Why is there one fewer tread than risers?
Each riser lifts you one step, but the top riser lands on the upper floor — that landing is not a tread. A stair with 17 risers has 16 treads.
What is the 2×riser + going rule?
A comfortable stair satisfies 2 × riser + going ≈ 63 cm. With a 17.65 cm riser and 25 cm going: 2 × 17.65 + 25 = 60.3 cm. Most codes cap risers at 19–20 cm and set a minimum going; always check local regulations.
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