CARPENTRY
Calculate stair rise and run, riser count, tread count, riser height and angle. Enter your measurements below and the estimate updates instantly.
Formula, validation and worked example reviewed November 12, 2026. See our calculation methodology.
Total run 11.67 ft · Step slope 35.8°
14 separate treads; upper landing not included in total run.
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Layout math and safety
This stair rise-and-run calculator rounds the riser count up so the actual riser height does not exceed your target, then uses one fewer tread than risers for a typical floor-to-floor flight.
Every step in a stair flight must have the exact same vertical riser height so users do not trip. To keep the actual step height at or below your maximum target riser (typically 7.5 in or 7.75 in), divide total floor-to-floor rise by the target riser and round up to the next whole integer:
where:
Riser count = round total rise / target riser up to a whole numberActual riser height = total rise / riser countTotal run = (riser count - 1) x tread depthStep slope = arctangent(actual riser height / horizontal tread going)Based on a 7.5 in maximum target riser and one fewer tread than risers.
| Total Floor Rise | Riser Count | Actual Riser Height | Total Run (@ 10 in Tread) |
|---|---|---|---|
| 36 in (3 ft deck) | 5 risers | 7.20 in | 40 in (3.33 ft) |
| 60 in (5 ft porch) | 8 risers | 7.50 in | 70 in (5.83 ft) |
| 96 in (8 ft ceiling) | 13 risers | 7.38 in | 120 in (10.00 ft) |
| 108 in (9 ft floor-to-floor) | 15 risers | 7.20 in | 140 in (11.67 ft) |
| 120 in (10 ft floor-to-floor) | 16 risers | 7.50 in | 150 in (12.50 ft) |
Divide the total rise into equal risers, then multiply the number of separate treads by the chosen tread depth. This calculator performs both steps and reports the resulting angle.
Under IRC Section R311.7.5.1, the maximum riser height is 7-3/4 inches (197 mm). Commercial codes under IBC typically require a 7-inch maximum riser.
A common carpentry rule of thumb is that 2 × rise + 1 × run should equal between 24 and 25 inches (for example, two 7.5" risers + one 10" tread = 25").
Rounding up creates more, shorter risers so the actual riser height stays at or below the target entered.
In a typical floor-to-floor flight, the upper floor or landing acts as the final walking surface, leaving one fewer separate tread.
No. It calculates geometry only. Verify riser, tread, width, headroom, landing, guard, handrail, and local requirements before building.
Flooring, decking, or landing thickness can change the first or last riser and create an unsafe height difference.
Use it as a planning starting point. Confirm the complete layout, board capacity, notch geometry, supports, attachments, and code before cutting.
Design safe, code-compliant stairs with uniform riser heights and tread runs before cutting any timber or pouring concrete.
Under the International Residential Code (IRC R311.7.5.1), maximum individual riser height is 7-3/4 inches (197 mm) to prevent tripping hazards.
The minimum horizontal tread depth is 10 inches (254 mm) nosing-to-nosing (or 11 inches if no nosing overhang is provided).
IRC code requires that the difference between the greatest and smallest riser or tread in a single flight must not exceed 3/8 inch (9.5 mm).
Measure total vertical rise from the top of the finished deck surface straight down to the solid landing pad (concrete or patio pavers) using a level and plumb board.
Method references: OSHA stairway construction requirements · American Wood Council deck stair guide