A shorter riser can need a longer stair.
An original hypothetical layout comparison—not an approved design, construction cut list or assertion that the example dimensions meet your local code.
Check your rise, run and available space →The measurements
Assume 108 inches between finished floors, a 10-inch entered tread depth and 144 inches of available straight run. The upper floor acts as the final walking surface. Landings, nosing, headroom, opening geometry and structural details are not included.
Compare two targets
| Entered maximum target | Risers | Actual equal rise | Treads | Run at 10 in |
|---|---|---|---|---|
| 7.5 in | ceil(108 ÷ 7.5) = 15 | 108 ÷ 15 = 7.2 in | 14 | 140 in |
| 7 in | ceil(108 ÷ 7) = 16 | 108 ÷ 16 = 6.75 in | 15 | 150 in |
The first geometry leaves four inches of the entered straight-run allowance; the second exceeds it by six inches. “Fits” means only that this arithmetic run is no greater than the entered allowance. It does not confirm a usable landing, headroom, safe construction or compliant stair.
Do not solve a tight space by ignoring requirements
Reducing tread depth or changing riser targets changes the arithmetic, but does not establish an acceptable design. Ask a qualified designer or contractor to evaluate the complete layout if the straight run is insufficient. Landings or turns require their own geometry; this single-flight example does not model them.
Measure finished surfaces, account for flooring thickness, and check the consistency of every riser, including the first and last. A rounded count is not a permission to cut a stringer.
What has been checked
These are original CalcCaddy arithmetic examples covered by tests of equal-rise division, whole riser counts, tread counts and available-run comparison. They deliberately do not quote universal building-code limits. Local adoption, building type and details control the applicable requirements.
Read the broader stair checks · Try both targets · Editorial standards.