Stair Calculator
Floor-to-floor height. Typical residential = 96-120 in.
IRC max: 7.75 in. Comfortable: 7-7.5 in.
Risers
15
Riser height
7.33″
Tread depth
10.33″
Stringer
181.74″
IRC code (US residential): ✓ compliant (max riser 7.75″, min tread 10″)
2R + T rule: ✓ comfortable (25, target 24-25)
Total run: 144.67″ (12.06 ft) — horizontal space needed for the stair on the floor.
2R + T rule: ✓ comfortable (25, target 24-25)
Total run: 144.67″ (12.06 ft) — horizontal space needed for the stair on the floor.
Stringer length from Pythagorean theorem: √(rise² + run²) — order 2×12 lumber at least this long, plus margin for cuts. The stringer is the structural board that holds the treads and risers.