Free planning calculator
Stair rise and run calculator
Work out how many risers a floor-to-floor height needs, what each riser actually measures, and how much floor length the flight consumes.
Direct answer
Divide total rise by a target riser height and round to a whole number of risers, then divide total rise by that count to get the actual riser. A straight flight has one fewer tread than risers, so total run is (risers - 1) x tread depth before landings are added.
Interactive tool
Enter your measurements
Formula
Worked example
A 108 in floor-to-floor rise with a 7.5 in target gives 108 / 7.5 = 14.4, which rounds to 14 risers. The actual riser becomes 108 / 14 = 7.714 in. Fourteen risers produce 13 treads, so a straight flight at 10 in per tread needs 130 in of floor length before landings, door swings, and headroom are reserved.
Assumptions
- The flight is straight, with equal risers and equal treads.
- Total rise is measured between finished floor surfaces.
- Landings, winders, and turns are planned separately from this run length.
Caveats
- Maximum riser, minimum tread, width, headroom, handrail, and guard requirements come from the locally adopted code, not from this arithmetic.
- Unequal risers within one flight are a recognized trip hazard and are restricted by code.
- Framing, finish thickness, and floor build-up change total rise; re-check after the floor assembly is decided.
Primary references
- 2024 International Residential Code: Building PlanningInternational Code Council; accessed 2026-08-02.
- ADA Accessibility Standards and GuideU.S. Access Board; accessed 2026-08-02.
Understand and continue
Stair rise and run: how to calculate a staircase
Turn a floor-to-floor height into a riser count, an actual riser height, a total run, and the floor space a flight really needs.
Read supporting guideTwo-story starter-home concept
A compact stacked footprint that keeps the stair and wet zones near the center for coordination.
Open starting concept