Rise and run
Total rise
Floor-to-floor. 8 ft = 96 in. How many steps for an 8-foot rise? 96 / 7.5 = 12.8 → 13 risers, 12 treads.
Target unit rise
Risers = round(total rise / this target). Actual unit rise is then total rise / risers, so 96 in lands at ≈ 7.385 in, not 7.5 on the nose.
Unit run (tread depth)
Default 10 in. Total run = treads × unit run. Nosing is out of scope.
Stringer layout
- Risers
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- Treads risers − 1
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- Unit rise
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- Stringer
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Enter total rise in inches. 8 ft is 96 in. Treads = risers − 1.
This is layout math, not an inspection and not a permit or code check. The 7.75 in flag is a common US residential IRC rule of thumb — it flags, it does not block. Not a staircase quote, not headroom, not nosing. Confirm with the AHJ. Nothing on this page leaves the browser.
How stringer layout is counted
People count risers and treads the same. They are not. Treads = risers − 1. Round the rise into risers, then the actual unit rise is total rise divided by that count so the stack hits the landing.
risers = round(total_rise / target_unit_rise) treads = risers − 1 actual_unit_rise = total_rise / risers stringer ≈ sqrt((risers × unit_rise)² + (treads × unit_run)²) 96 in, 7.5 target, 10 run: 96 / 7.5 = 12.8 → 13 risers 12 treads 96 / 13 ≈ 7.385 in unit rise stringer ≈ sqrt((13×7.385)² + (12×10)²)
An 8-foot (96 in) rise is 13 risers and 12 treads, not 13 of each.
FAQ
Why are there fewer treads than risers?
Number of TREADS = risers − 1. That's the gotcha; people count them the same. A flight that climbs on 13 risers has 12 treads — the last riser lands on the upper floor, which is not a tread you cut. Same math for any count: treads = risers − 1 always.
How many steps for an 8-foot (96 in) rise?
96 in total rise at a 7.5 in target unit rise: 96/7.5 = 12.8, which rounds to 13 risers. Actual unit rise is 96/13 ≈ 7.385 in, and treads = 13 − 1 = 12. Default unit run 10 in. That is the 8-foot-rise fixture this tool is built around.
How do you pick the number of risers?
Number of RISERS = round(total rise / target unit rise). Then the actual unit rise is total rise divided by that count, so the stack hits the landing. 96/7.5 = 12.8 → 13 risers, unit rise 96/13 ≈ 7.385 in — not 7.5 on the nose.
How is stringer length calculated?
Stringer length ≈ sqrt((risers × unit rise)² + (treads × unit run)²). For the 96 in fixture with 13 risers, 12 treads, and a 10 in unit run: sqrt((13×7.385)² + (12×10)²). That is the hypotenuse of total rise and total run. It is a board length for layout, not a cut list with birds-mouth waste.
What does the 7.75 in flag mean? Is this a code check?
If actual unit rise is over 7.75 in, the tool flags it — it does not block the math. 7.75 in is a common US residential IRC ballpark for riser height. It is labeled as a rule of thumb, NOT a permit or code check. This is layout math, not an inspection. Confirm with the AHJ.
Is this a staircase quote? Does it cover headroom or nosing?
No. Not a staircase quote, not headroom, not nosing detail. Rise/run layout only: riser count, tread count (always risers − 1), unit rise, unit run, and stringer hypotenuse. Empty inputs are invalid, not a layout. Related tools: board feet, drywall, and the Acorn hub.