VolunaroStair calculator
How the calculation works
- Risers: we divide the total rise by your target riser height and round to the nearest whole number, because a stair needs equal risers.
- Real riser height: the total rise divided by that number of risers, so every step is the same height.
- Treads: one fewer than the risers, because the upper floor is the last step. Total run is the treads times the tread depth.
- Stringer: the diagonal length from the lower floor to the upper floor, found with the Pythagorean theorem on the total rise and total run.
Worked example
A stair between floors 108 in (9 ft) apart, with a 7 in target riser and 10 in treads.
- Risers (steps up)
- 15
- Actual riser height
- 7.20 in
- Treads
- 14
- Total run
- 11.67 ft
- Stringer length
- 14.73 ft
Default values and sources
| Value | Default | Type | Sources |
|---|---|---|---|
| Target riser height for a stair | 7 in | Our default (editable) | — |
| Tread depth for a stair | 10 in | Our default (editable) | — |
Limitations
- Building codes set limits on riser height, tread depth and uniformity, and they differ by place and by use. Check your local code and your inspector before you cut anything.
- This tool lays out a straight stair between two finished floors. It does not design landings, winders or curved stairs, and it does not size the stringers or check their strength.
- Measure the total rise from finished floor to finished floor. If the flooring on either level is not installed yet, allow for its thickness.
Results are estimates for planning and ordering, not professional, engineering or legal advice. Confirm quantities, sizes and local building requirements with your supplier or contractor before you buy or build.