Stair Rise & Run Calculator
Unit rise = total rise ÷ risers; angle = atan(rise/run). Click any i for detail.
Stair geometry
Total rise (in)
i
Rise
Floor-to-floor height. |
|
|---|---|
Number of risers
i
Risers
Count of risers (treads ≈ risers − 1). |
|
Tread run (in)
i
Run
Horizontal depth of each tread (unit run). |
How to use this calculator
- Measure total floor-to-floor rise.
- Choose number of risers.
- Enter tread run.
- Read unit rise, angle, and stringer sketch — then check code.
Results explained
Uniform risers divide total rise evenly. Stair angle follows atan(rise/run). Stringer length is approximated from total rise and run × number of treads. Local codes set max rise and min tread.
Quick reference: stairs
rise = totalRise / numRisers; θ = atan(rise/run).
| Item | Detail |
|---|---|
| Typical rise | Often ~7–7.75 in (check code) |
| Treads | Usually risers − 1 |
| Steeper angle | Harder climb |
| Stringer | Hypotenuse sketch |
Confirm IRC/local code before cutting stringers.
How the estimate is built
rise = totalRise/numRisers; angle = atan(rise/tread); stringer ≈ hypot(totalRise, tread×(risers−1)).
Example scenario
108 in / 14 risers → unit rise 7.71 in with 10 in run.
FAQ
Why risers − 1 treads?
Top landing usually isn’t a tread.
Nose overhang?
Run may be measured differently — follow your code definition.
Metric?
Convert consistently to inches or scale all fields.
Winder stairs?
Not modeled.