Calculator
Example data table
| Total rise (in) | Risers | Actual riser (in) | Treads | Total run (in) | Actual tread (in) | Angle (deg) |
|---|---|---|---|---|---|---|
| 108 | 14 | 7.714 | 13 | 130 | 10.000 | 37.6 |
| 96 | 13 | 7.385 | 12 | (estimated) | 9.730 | 37.2 |
| 120 | (auto) | 7.500 | 15 | 165 | 11.000 | 34.3 |
Formula used
- Actual riser height: R = Total Rise ÷ Number of Risers
- Typical tread count: Treads = Risers − 1 (can be overridden)
- Actual tread depth: T = Total Run ÷ Number of Treads
- Comfort rule range: 2R + T ≈ 24–25 inches (converted for metric)
- Going: Going = T + Nosing (optional)
- Stair angle: θ = arctan(R ÷ T)
- Stringer length: L = √(Total Rise² + Total Run²)
How to use this calculator
- Select units, then enter the total rise between finished floors.
- Choose riser mode: enter riser count, or target riser height.
- Choose tread mode: use total run, set tread depth, or estimate.
- Add nosing, width, and thickness if you need takeoffs.
- Adjust limits to match your project’s rules, then calculate.
- Download CSV or PDF to share with your crew and client.
Practical guide to stair treads
1) Why tread sizing matters
Tread depth controls footing, walking rhythm, and how confidently people descend. In residential work, designers often target 10–11 inches of tread depth with risers around 7–7.75 inches, then verify comfort using a simple rule. Consistent dimensions are as important as the averages, because irregular steps increase trips.
2) Key inputs used by the calculator
The most reliable starting point is the finished floor-to-floor rise. From there, you can either set an exact riser count or a target riser height and let the tool determine the count by rounding up. If you know the available horizontal space, add total run to compute tread depth directly; otherwise, the calculator estimates tread depth using a comfort guideline.
3) Comfort rule and tread range
A widely used field check is the comfort rule: 2R + T ≈ 24–25 inches. After the calculator finds the actual riser height R, it reports a recommended tread range. For example, if R is 7.5 inches, the comfort range suggests T near 9–10 inches. This helps you judge whether a layout feels steep or relaxed before committing to framing.
4) Angle and overall geometry
Stair angle is computed from arctan(R ÷ T). Many comfortable residential stairs land roughly in the mid‑30° range, while steeper runs can push toward the high‑30s. The stringer length is the diagonal between total rise and total run, which is useful for rough material planning and verifying that stock lengths are practical on site.
5) Run, going, and nosing
Total run is the sum of tread depths across the flight. “Going” can include nosing projection when you want a more realistic step footprint. If nosing is used, the calculator reports both tread depth and going so you can align layout lines, confirm finish overhang, and coordinate with trim and flooring thicknesses.
6) Simple code checks you can tune
Projects vary by jurisdiction and occupancy, so the calculator keeps the limits editable. By default it checks riser height against 7.75 inches and tread depth against 10 inches, then flags PASS or FAIL. Treat these as screening checks and confirm final compliance with your local rules and any project-specific accessibility requirements.
7) Material takeoffs from width and thickness
When stair width is provided, the tool estimates area per tread and total tread area, helpful for coatings, tile, or tread coverings. Add tread thickness to estimate volume, which supports lumber selection or concrete/stone planning. Output units adapt automatically: square feet or square meters, cubic feet or cubic meters.
8) Workflow for dependable layouts
Start with finished dimensions, then iterate: choose riser mode, review the resulting tread range, and adjust until both the comfort rule and your limits pass. Use rounding for field-friendly values, but keep the total rise exact so the top landing meets finish elevation. Finally, export CSV or PDF to share layout assumptions with your crew and client.
FAQs
1) Should treads equal risers minus one?
Usually yes for a single straight flight: one fewer tread than risers. Landings, winders, and split flights can change the count, so override treads when your layout includes those conditions.
2) What if my total run is fixed?
Enter the total run to compute the actual tread depth from your space constraint. Then check the comfort rule range and adjust riser count or target riser height until the stair feels comfortable and passes your limits.
3) Why does the tool estimate tread depth sometimes?
If you leave total run blank, the calculator uses the comfort rule midpoint to suggest a tread depth and the resulting run. This gives a practical starting point when early planning is based on rise only.
4) How do I use metric inputs?
Select metric and enter rise, run, and limits in millimeters. Internally the calculator converts to inches for rules, then converts results back to millimeters so the comfort guidance remains consistent across unit systems.
5) What does “going” mean here?
Going is the step footprint used for walking, calculated as tread depth plus any nosing projection you enter. It helps compare layouts where finish overhang is significant.
6) Can I round to common tape marks?
Enable rounding to nearest 1/16 for imperial layouts. Use rounding for step dimensions, but keep the total rise accurate and recheck the final top riser so the finished landing elevation remains correct.
7) Are the default limits always correct?
No. The defaults are common residential screening values, not universal rules. Always verify requirements for your location, occupancy type, and accessibility standards, then enter the applicable limits before finalizing.
Measure twice, compute once, then build safer stairs today.