Stair Calculator
Enter the total height your stairs must climb and your preferred tread depth to get the number of steps, the exact riser height, the total run, and a quick comfort check.
Comfortable, safe stairs come down to two measurements: the riser (how tall each step is) and the tread (how deep it is). Given the total height you need to climb, this calculator finds a whole number of steps that keeps the riser in the comfortable 7–7¾ inch range, then works out the tread run and checks it against the classic stair-building rules.
How to calculate stairs
Divide the total rise by a comfortable target riser (about 7½ inches) and round to a whole number of risers. Dividing the total rise by that count gives the exact riser height. There's always one fewer tread than riser, so the total run is the number of treads times the tread depth.
Riser height = Total rise ÷ Number of risers
Treads = Risers − 1 · Total run = Treads × Tread depth
| Rule of thumb | Comfortable range |
|---|---|
| Riser height | 7 – 7¾ in (max ~7.75 by code) |
| Tread depth | 10 – 11 in (min ~10 by code) |
| 2 × riser + tread | 24 – 25 in |
| Riser + tread | 17 – 18 in |
Worked example
A total rise of 108 inches (9 ft) with 10-inch treads:
| Risers = round(108 ÷ 7.5) | 14 |
| Riser height = 108 ÷ 14 | 7.71 in |
| Treads = 14 − 1, run = 13 × 10 | 130 in |
| 2 × 7.71 + 10 | 25.4 in (in range) |
Reading the comfort check
The "2 × riser + tread" figure should land between about 24 and 25 inches for a stride that feels natural — too low and the stairs feel shallow and long, too high and they feel steep. If your result falls outside the range, nudge the tread depth or accept one more (or fewer) step and recalculate. Always confirm the final riser and tread against your local building code, which sets legal maximums and minimums.