Stair Calculator
Estimate stair risers, actual riser height, treads and horizontal run from total rise
Use this for planning only. Verify stair dimensions against your local building code before construction.
Required risers
How we calculated it
About the Stair Calculator
Stair layout turns a total vertical rise into a practical number of risers and matching tread geometry. Small changes in riser count can change the height of every step, so the layout should be solved as a whole.
This calculator is a planning aid. Final stairs must comply with the building code, headroom, landing and handrail requirements that apply to the project.
How to Use the Stair Calculator
- Measure the total finished-floor-to-finished-floor rise.
- Enter a target or maximum riser height according to the design criteria you are using.
- Enter tread or run requirements when supported.
- Calculate whole riser count and actual riser height, then verify the final geometry against applicable code.
How the Calculation Works
Initial riser count is total rise ÷ target riser height, then adjusted to a whole number. Actual riser height = total rise ÷ whole riser count.
Total run is based on the number of treads multiplied by tread depth, with the tread count depending on whether the stair ends at an upper floor or landing.
Worked example
Stair Calculator Worked Example
Total rise 108 inches with about 7-inch risers
108 ÷ 7 ≈ 15.43, so a practical layout may use 16 risers. Actual riser height = 108 ÷ 16 = 6.75 inches. The tread count and total run are then based on that final riser layout.
Result guide
Understanding Your Stair Calculator Result
Do not round riser height independently after choosing the count. All risers should be laid out from the same total rise so the finished heights remain consistent.
Before you rely on the answer
Assumptions and Limitations
- Total rise is measured between finished floor surfaces.
- Whole riser count is required.
- Code limits, nosing, landings, headroom and structural design are checked separately.
Practical tip
Using This Result in Practice
Measure after accounting for finished flooring thickness at both levels. A small floor-finish change can create an inconsistent first or last riser if it is ignored.
Related calculations
Useful Calculations to Continue With
If you are checking the overall rise-to-run relationship, the Slope Calculator can help describe the stair inclination mathematically.
If you need the diagonal stringer length from total rise and run, use the Pythagorean Theorem Calculator.
Common questions
Stair Calculator FAQ
Why must stair risers be a whole number?
A staircase consists of complete risers, so the total rise must be divided among an integer number of steps.
Why recalculate the actual riser height?
The target height is only a starting point. Once a whole riser count is chosen, total rise is divided evenly by that count.
Can this calculator confirm building-code compliance?
No. Code requirements vary and include more than riser and tread dimensions.