CalcCommonsHow to use
Measure from the lower finished floor to the upper finished floor. Choose a desired maximum riser or supply a riser count. Enter the horizontal tread going, then review the resulting layout before discussing construction details with a qualified builder.
For related tasks, try the Roof Pitch Calculator.
Formula & how it works
Risers = round up(total rise ÷ desired maximum riser), minimum 2. Actual riser = total rise ÷ risers. Treads = risers − 1. Run = treads × going. Step pitch = arctan(actual riser ÷ going).
Worked examples
Example 1
With 108 in of finished-floor rise and a desired maximum riser of 7.5 in, use 15 risers at 7.2 in each. The upper floor is the last landing, so 14 treads at 10 in going require 140 in of horizontal run.
Example 2
For a 2.8 m rise with 16 selected risers, each riser is 0.175 m. Fifteen treads at 0.28 m going require a 4.2 m horizontal run.
Assumptions & practical notes
The top floor serves as the final tread. Designs with a separate top tread, intermediate landings, winders or spiral stairs need a different layout.
The floor-to-floor diagonal joins the lower and upper floor endpoints. It is not the cut length of a stringer; end cuts, bearing, nosing and tread thickness change that detail.
Desired riser height is a user setting, not a local code rule. Check headroom, clear width, landings, riser consistency, handrails and applicable requirements with your local building department.
See our calculation methodology for unit definitions and testing practices.
Results are estimates for planning purposes. Verify measurements, product specifications, and applicable building codes before purchasing materials or starting work.
References & measurement guidance
Use the instructions for your selected product and the requirements that apply to your project. Example inputs are not universal specifications.
Frequently asked questions
Why are there fewer treads than risers?
The top finished floor serves as the final stepping surface in this model. A flight with 15 risers therefore has 14 separate treads.
What is tread going?
Going is the horizontal distance from one tread nosing to the next. It can differ from the physical tread board depth when there is an overhang.
Does this verify building code compliance?
No. It calculates geometry only. The calculator does not determine which code applies or check headroom, width, landings or guards.
Can I cut a stringer using the diagonal result?
No. The result is an overall planning diagonal. A stringer layout requires the actual tread/riser assembly and end bearing details.
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