For a level guard section beside a landing, use the baluster spacing calculator to get equal gaps and center marks. It does not lay out balusters on a sloping stair rail.
What the stair calculator returns
This stair calculator divides a measured floor-to-floor rise into equal risers, using your target riser height. You supply the tread depth. The results show riser count, actual riser height, tread count, total horizontal run, stair angle and inclined stringer layout length.
The upper floor acts as the final tread in this model. It describes a straight flight; it does not design winders, spiral stairs or intermediate landings.
Enter your stair measurements
- Total rise: vertical distance between the finished lower and upper floor, in inches or millimeters.
- Tread depth: the horizontal step going you want to use, in the selected units. This is not the depth of a board including an added nosing.
- Target riser height: the preferred height used to choose a whole number of risers. The actual equal height may differ.
The tool uses round(total rise ÷ target riser), not an automatic search for a compliant design. Add available horizontal run if you want a space check. Measure from the first riser to the upper-floor edge along the floor plan, reserving any required landing space separately. A positive remainder is unused horizontal run; a shortfall is extra run needed. Neither result checks headroom or confirms a suitable design. Leaving this field blank keeps the stair calculation available.
Inches or millimeters
Select mm to convert all current dimensions, including the optional available run. A 96-inch rise becomes 2438.4 mm; the riser and tread counts stay the same. Use decimal inputs for fractions: 10 1/2 inches is 10.5. Switching units changes the measurement system, not the local requirements that apply to your project.
The side view updates as you type. Its vertical dimension is the full floor-to-floor rise; its horizontal dimension spans the separate treads. The dashed line follows the repeated step slope. Use Copy results or Print results to keep the inputs, layout and assumptions together.
Worked example: a 96-inch rise
Enter a total rise of 96 inches, tread depth of 10.5 inches and target riser of 7 inches.
- Riser count = round(96 ÷ 7) = 14.
- Actual riser height = 96 ÷ 14 ≈ 6.857 inches.
- Tread count = 14 − 1 = 13.
- Total run = 13 × 10.5 = 136.5 inches.
- Stair angle = arctan((96 ÷ 14) ÷ 10.5) ≈ 33.1°.
- Inclined stringer layout length = 13 × √((96 ÷ 14)² + 10.5²) ≈ 163.03 inches.
The angle follows the repeated riser-and-tread geometry. Dividing the full floor-to-floor rise by total run gives a different angle because the upper floor accounts for the final riser without another separate tread.
If the available horizontal run is 144 inches, this example leaves 7.5 inches of run. At 132 inches, it needs 4.5 inches more. The tread depth remains 10.5 inches in either comparison.
How long are stairs for an 8-foot ceiling?
An 8-foot ceiling is not enough information to calculate the stairs. Measure between finished floors: the floor structure above the ceiling changes that vertical distance. If the measured floor-to-floor rise is exactly 96 inches, the example above applies. If it is 108 inches, a 7-inch target and 10-inch going produce 15 risers, 14 treads and a 140-inch run. Always enter the measured rise rather than assuming it from ceiling height.
Does this calculator include a landing?
It models one straight flight with the upper floor as the final tread. It does not insert intermediate platforms, design turning stairs or check clearances. Plan those details separately. For a level guard beside a landing, the baluster spacing calculator reports equal gaps and individual center marks.
Layout length is not stock length
Stringer layout length measures the inclined distance across the repeated tread segments. It excludes top and bottom end-cut details, bearing and spare material. Do not use it directly as a finished cutting length or a minimum board purchase length.
The stair stringer calculator uses the same geometry and adds an entered tread-thickness adjustment. A manufacturer example for this convention appears on page 19 of the Johnson CALC-1500 manual.
Read the reference checks carefully
The indicators compare riser height with 7.75 inches, tread depth with 10 inches and angle with a 30–37° reference range. These are limited planning checks, not a complete assessment of applicable building rules. In particular, the angle range is not presented as a universal code requirement.
Verify finished-floor details, available space, headroom, landings, handrails and structural requirements for your project. Read the calculation methods or send a correction if an input or result is unclear.
Good questions. Straight answers.
Does this tool choose a tread depth for my available space?
You choose the tread depth. Add an optional available horizontal run to see the space remaining or extra run needed. The tool does not automatically shorten treads or reserve landing space.
Why is there one fewer tread than risers?
This model uses the upper floor as the final tread. A flight with 14 risers therefore has 13 separate treads below that floor.
Do the indicators confirm building-code compliance?
No. The optional planning references compare three values with the tool's reference thresholds. Headroom, landings, handrails, structure and local requirements need separate review.