Stair Calculator
Plan stairs that are comfortable and code-friendly.
Your numbers
Your results
Number of risers
Number of risers
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Actual riser height (in)
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Total run (in)
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Stair angle (degrees)
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Comfort check (2 × riser + tread)
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Stair Calculator by TheCalcTools
How the Stair Calculator works
Measure the floor-to-floor height as the total rise.
Divide by your preferred riser height and round to a whole number of risers.
The actual riser is the total rise divided by that number; the run is one less tread than risers.
The formula
Risers = round(total rise ÷ preferred riser)Run = (risers − 1) × tread
Worked example
Using the default values shown in the calculator:
| Total rise (in) | 108 |
|---|---|
| Preferred riser height (in) | 7.5 |
| Tread depth (in) | 10 |
- 108 ÷ 7.5 = 14.4, so 14 risers of 7.714 in.
- Total run = 130.0 in, angle 37.6°, comfort check 25.4.
Result:
| Number of risers | 14 |
|---|---|
| Actual riser height (in) | 7.714 |
| Total run (in) | 130.0 |
| Stair angle (degrees) | 37.6 |
| Comfort check (2 × riser + tread) | 25.4 |
Frequently asked questions
What riser height do building codes allow?
Many codes cap risers at about 7¾ inches and require treads of at least 10 inches. Check your local code before building.
What is the 2R + T rule?
A comfort guide: twice the riser plus the tread should be about 24–25 inches.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.