2408
Stair calculator
Put your total rise, riser height and tread depth in: a 96 in rise at 7.5 in per riser needs 13 risers at 7.38 in each — 12 treads, 120 in of run.
★ CONSTRUCTION · STAIRS · STEPS
Stair Calculator: 13 Risers, 7.38 in Each, 96 in Rise
On the defaults — a 96 in rise, 7.5 in riser, 10 in tread — you need 13 risers at 7.38 in each. This is the stair tool: measure the rise once, divide it into equal steps, and cut the stringers once — a half-built staircase waits for no second delivery.
What does stairs need 13 risers mean?
It means the staircase climbs 96 inches in 13 equal steps of 7.38 inches each. The desired riser was 7.5 inches, and 96 divided by 7.5 is 12.8 steps — but steps are whole, so the count rounds up to 13, and the rise is then shared equally: 96 divided by 13 is 7.38 inches per riser. There are 12 treads, one fewer than the risers, because the top step lands on the upper floor itself, and at 10 inches per tread the staircase runs 120 inches, or 10 feet, from the first riser to the landing.
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| Risers | total rise ÷ desired riser, rounded up | 13 risers — 96 ÷ 7.5, rounded up. |
| Actual riser | total rise ÷ risers | 7.38 in — 96 ÷ 13. |
| Total run | (risers − 1) × tread depth | 120 in — 12 × 10. |
Three things to check before you trust the number
First, check the rise you measured: it is floor to floor, finished floor to finished floor, and a rise measured to the subfloor under-counts by the flooring thickness. Second, keep the risers equal: the whole point of dividing the rise by the rounded count is that every step is the same height, and one odd step trips everyone who uses the stairs. Third, judge the run honestly: 120 inches is 10 feet of floor, and a staircase that fits the rise but not the run needs a landing or a turn, not a steeper riser. Check the deck board calculator for the deck these stairs may land on.
Worked example
96 in rise, 7.5 in desired riser, 10 in tread. Risers: 96 ÷ 7.5 = 12.8, rounded up to 13 risers. Actual riser: 96 ÷ 13 = 7.38 in. Treads: 13 − 1 = 12. Total run: 12 × 10 = 120 in, or 10 ft. In practice that means cutting 13 risers at 7.38 in each and laying 12 treads at 10 in deep, with the top tread being the upper floor itself. If the same rise used a 7 in riser instead, the need would rise to 14 risers at 6.86 in each, and the run to 130 in — the rise alone would be identical.
Every branch, checked
With a 108 in rise instead of 96 in, the count rises to 15 risers at 7.2 in each, and the run to 140 in. With a 7 in riser, the count rises to 14 risers at 6.86 in each, and the run to 130 in. With an 11 in tread, the count stays 13 risers but the run stretches to 132 in, since tread depth moves only the run. With an 8 in riser, the count falls to 12 risers at 8 in each, and the run to 110 in. Rise, riser and tread each move the answer on their own, so a wrong rise is as costly as a wrong riser.
The reverses, worked backwards
The rise behind 13 risers is 96 in: at 84 in the need is 12 risers (7 in actual riser, 11 treads, 110 in total run); at 108 in it is 15 risers (7.2 in actual riser, 14 treads, 140 in total run). The riser behind 13 risers is 7.5 in: at 7 in the need is 14 risers (6.86 in actual riser, 13 treads, 130 in total run); at 8 in it is 12 risers (8 in actual riser, 11 treads, 110 in total run). The tread behind 13 risers is 10 in: at 9 in the run is 108 in; at 11 in it is 132 in, and the riser count does not move at all. Each reverse moves one input and holds the rest, so the step is exactly one rise, riser or tread change.
What the defaults assume
The defaults assume a straight staircase climbing 96 inches, a 7.5 in desired riser, and 10 in treads. They do not assume a landing, a turn, handrails or stringers — a staircase that needs a landing splits the rise across two flights, and the handrail and stringer lengths are bought separately, not by the step.
Who uses this
- A homeowner building deck stairs: the 13-riser count settles the stringer layout before the first board is cut.
- A DIY builder framing a basement stair: the same maths on the floor-to-floor rise gives the steps, not a whole house.
- A contractor quoting a staircase: rise, riser, tread — the quote follows the same three steps, and the equal-riser line shows the client why.
- A landlord budgeting a stair refit: the rise off the plans, divided and rounded up, gives the step line on the refit budget.
Accuracy & limitations
The arithmetic is exact for the inputs entered; the judgement is the rise measurement and the riser target. Real stairs must meet local code on riser height and tread depth, and the lumber on the shelf overrides any planning figure; a rise measured to the subfloor under-counts, and a riser target read off a different staircase builds uneven steps. Treat 13 risers as the planning count for a 96 in rise at 7.5 in, and check the code maximum riser before cutting.
Cite this calculator
Bright Side Kit, “Stair Calculator: 13 Risers, 7.38 in Each, 96 in Rise”, https://brightoolbox.com/stair-calculator/, accessed 3 November 2026. Students and researchers: cite the calculator name, the page URL and the date you used it, and quote the defaults (96 in rise, 7.5 in riser, 10 in tread) so the 13-riser result can be checked.
Frequently asked questions
How many steps do I need for a 96 in rise?
13 risers at 7.38 in each, with a 7.5 in desired riser. The count is 96 ÷ 7.5 = 12.8, rounded up to 13, and the rise is then shared equally.
How do I work out stair steps from a total rise?
Divide the total rise by the desired riser height and round up, then divide the rise by the rounded count for the actual riser. A 96 in rise at 7.5 in gives 13 risers at 7.38 in each.
Why is the actual riser not the riser I entered?
Because steps are whole: 96 ÷ 7.5 is 12.8 steps, which rounds to 13, and 96 ÷ 13 is 7.38 in. Equal risers matter more than hitting the target exactly.
How many treads does a staircase have?
One fewer than the risers: 12 treads for 13 risers. The top step lands on the upper floor itself, so it is not a tread.
Does tread depth change the step count?
No — tread depth moves only the total run. An 11 in tread on the same stairs stretches the run from 120 in to 132 in and leaves the count at 13 risers.
Should I measure rise floor to floor or subfloor to subfloor?
Finished floor to finished floor. A rise measured to the subfloor under-counts by the flooring thickness on both floors.