Stair Calculator
Risers are ceil(total rise / max riser), at least 2. Treads equal risers minus 1. Optional total run yields tread depth and 2R+T. This is not building-code approval.
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How to estimate stair risers and treads
- Enter total rise from finished floor to finished floor in inches, centimeters, or millimeters.
- Enter the maximum riser you will allow, such as 7.75 in.
- Read riser count, equal riser height, and tread count (risers minus 1).
- Optional: enter total run for tread depth and 2R+T. Confirm with local rules. This is not code approval.
Stair geometry
Equal risers from a max riser cap
| Risers | max(2, ceil(rise / maxRiser)) |
|---|---|
| Riser height | total rise / risers |
| Treads | risers minus 1 |
| Tread depth | total run / treads when run is set |
| 2R+T | 2 × riser + tread |
| Advice | Not building-code approval |
How risers, treads, and 2R+T are computed
Riser count is the ceiling of total rise over max riser, never below 2. Each riser is total rise divided by that count. Treads are one less than risers. If you type total run, tread depth is run over treads, and 2R+T is two risers plus one tread. The unit list labels the numbers you typed. It does not convert 108 inches into centimeters.
Riser, tread, and 2R+T
2R+T is a common comfort check in inches, not a permit. Roof slope is roof pitch. Site percent grade is grade. Floor area is square footage.
Not building-code approval
Codes cap riser height, tread depth, nosing, and headroom. This page does not load those tables. A builder and the authority having jurisdiction own the stair. Estimate only.
Use cases
A 9 ft floor-to-floor rise, checking 7.75 in as a cap, or seeing 2R+T after you tape the run. Winders and landings are not modeled.
Limits
Rise and max riser must be greater than 0. Units label the output only. CZNull does not receive the numbers.