Staircase Calculator
Steps = total rise ÷ target riser (7.75 in)
How Staircase Calculations Work
Stair design balances total rise (floor-to-floor height) and total run (horizontal footprint). The number of steps = total rise ÷ target riser height. A 9 ft (108 in) floor-to-floor change with a 7.75 in target riser gives 108 ÷ 7.75 ≈ 14 steps. Actual riser height = 108 ÷ 14 = 7.71 in per step — uniform risers are critical for safety.
Tread depth = total run ÷ (steps − 1). With 14 steps there are 13 treads (the top landing is the 14th step level). A 10 ft (120 in) total run yields 120 ÷ 13 = 9.23 in tread depth. Building codes typically require 7–7.75 in max riser and 10 in min tread (IRC). The sum of one riser and one tread should fall between 17 and 18 in for comfortable stride — 7.71 + 9.23 = 16.94 in, slightly tight; widening run improves comfort.
Stringer length = √(rise² + run²) = √(108² + 120²) = √(11,664 + 14,400) = √26,064 = 161.4 in (13.45 ft) per stringer. Cut three stringers for a standard residential stair — two outer plus one middle support. Headroom must be at least 6 ft 8 in measured vertically from tread nosing — critical in basement stairs under floor joists.
Concrete stair volume can be estimated separately using the concrete calculator's stair shape input. Handrail height is 34–38 in above tread nosing. Open risers are prohibited in many jurisdictions for residential use. Always verify local code amendments before construction.
| Total Rise | Total Run | Steps | Riser | Tread |
|---|---|---|---|---|
| 9 ft (108 in) | 10 ft (120 in) | 14 | 7.71 in | 9.23 in |
| 8 ft (96 in) | 9 ft (108 in) | 12 | 8.00 in | 9.82 in |
| 10 ft (120 in) | 11 ft (132 in) | 16 | 7.50 in | 8.77 in |
| 7 ft (84 in) | 8 ft (96 in) | 11 | 7.64 in | 9.60 in |
Enter total rise, total run, and optional target riser height to get step count, riser height, tread depth, and stringer length. Pair with the concrete calculator for poured stair volume estimates.
Examples
| Example | Result |
|---|---|
| 9 ft rise, 10 ft run, 7.75 in target riser | 14 steps, 7.71 in riser, 9.23 in tread |
| 8 ft rise, 9 ft run | 12 steps, 8.00 in riser, 9.82 in tread |
| 10 ft rise, 11 ft run | 16 steps, 7.50 in riser, 8.77 in tread |
| 7 ft rise, 8 ft run | 11 steps, 7.64 in riser, 9.60 in tread |
| 9 ft rise, 12 ft run (comfortable) | 14 steps, 7.71 in riser, 11.08 in tread |
| Stringer for 9×10 ft stair | ~161 in (13.45 ft) per stringer |
| Basement 8 ft rise, 9 ft run | 12 steps, 8 in riser |
Frequently asked questions
Residential codes cap risers at 7.75 inches. A consistent 7 to 7.5 inch riser with a 10+ inch tread is comfortable for most users.
Steps include the landing level; treads are the horizontal surfaces you walk on. A 14-step staircase has 13 treads plus the top floor level.
Stringer length is the hypotenuse: √(total rise² + total run²). This is the diagonal board that supports treads and risers.