🪜 Stair Calculator
Measure the total height from finished floor to finished floor in inches, and choose your tread depth.
How the Stair Calculator works
The rise is divided into equal steps no taller than 7¾ inches (the US residential code maximum). There is one fewer tread than risers. Tread depth should be at least 10 inches.
Step-by-step calculation
- 1Measure total rise.
- 2Divide into equal risers no taller than 7¾ inches.
- 3Treads = risers − 1.
- 4Find total run, angle and stringer length.
Worked example
A 108-inch rise needs 14 risers of 7.71 inches and 13 treads. With 10.5-inch treads the run is 136.5 inches, the angle is about 36°, and the stringer is about 174 inches.
Stair Calculator examples
| Total rise (inches) | Stair layout |
|---|---|
| 54 | 7 risers of 7.71" |
| 81 | 11 risers of 7.36" |
| 108 | 14 risers of 7.71" |
| 135 | 18 risers of 7.5" |
| 162 | 21 risers of 7.71" |
Other inputs kept at the calculator's default values. Results calculated by this calculator.
Why use a Stair Calculator?
Lay out safe, code-friendly stairs.
Important factors that can affect your results
- Local building codes.
- Finished floor thickness.
- Headroom clearance.
Frequently asked questions
What are the code limits?
The US IRC allows risers up to 7¾ inches and requires treads of at least 10 inches. Local codes may differ.
Why is there one less tread?
The top step is the upper floor itself.
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Last reviewed November 2026 · How we build and check our tools · Report a problem