Stair planning tool
Stair Calculator (Free Riser and Tread Plan)
A stair calculator divides the measured floor-to-floor rise into equal risers that do not exceed the preferred planning height entered. It then uses one fewer tread than risers to estimate horizontal run and the sloped stringer line.
This calculator is a planning estimate. Verify the actual site, product specifications and applicable local requirements before ordering or building.
How the calculation works
Riser count = total rise divided by preferred maximum riser, rounded up. Actual riser = total rise divided by riser count. Tread count = riser count minus one. Run = tread count multiplied by tread depth, plus any landing depth.
Worked example
A 108-inch floor-to-floor rise with a 7.5-inch preferred maximum creates 15 equal risers at 7.2 inches each. Fourteen 10.5-inch treads produce a 147-inch horizontal run before landings.
Reference table
| Input | Result | Use |
|---|---|---|
| 96 in rise | 13 risers | 7.38 in each |
| 102 in rise | 14 risers | 7.29 in each |
| 108 in rise | 15 risers | 7.20 in each |
| 114 in rise | 16 risers | 7.13 in each |
| 120 in rise | 16 risers | 7.50 in each |
Reference rows are examples, not product orders. Enter the measured project values in the calculator for a usable estimate.
How to use the result
- Measure finished surfaces, not rough framing, and record every obstruction.
- Enter the real product dimensions when the tool offers an editable width, length, repeat or coverage field.
- Compare the calculated result with the supplier label and round purchase quantities up only after checking package size.
- Mark the proposed layout on the wall before cutting, attaching or ordering custom pieces.
Frequently asked questions
How many steps are needed for a 9-foot rise?
With a 7.5-inch preferred maximum, a 108-inch rise produces 15 risers and 14 treads. Local rules may require a different result.
Why are there fewer treads than risers?
The upper floor normally acts as the final walking surface, so a straight flight has one fewer tread than vertical rises.
Does the calculator verify building code?
No. It is a planning estimator. Confirm rise, run, headroom, width, landings, guards and handrails with the current local authority.
What measurement should I use for total rise?
Measure vertically from the finished lower floor to the finished upper floor, including final flooring thicknesses.
Can I add a landing?
Yes. Enter the landing count and depth to add its horizontal length to the total run estimate.