Fire Egress Calculator

This calculator walks through the first stage of an IBC (International Building Code) egress-capacity check: converting a floor area into an Occupant Load, then sizing exits around that number. Occupant Load divides Floor Area by an occupant load factor (square feet per person) that depends on Occupancy Type -- 15 sf/person for unconcentrated Assembly seating, 150 for Business, 20 for an Educational classroom, 60 for Mercantile sales floors, and 100 for Industrial -- each a commonly-cited representative figure for that broad group under IBC Table 1004.5, though the real table subdivides each group further by specific use (assembly space alone ranges from 5 sf/person standing to 15 sf/person for tables and chairs). From Occupant Load, Minimum Exits Required steps up at the two IBC Table 1006.3.1 breakpoints -- 2 exits up to 500 occupants, 3 up to 1,000, 4 above that. Total Stair Width and Total Level Exit Width are Occupant Load times a per-occupant inch factor from IBC Table 1005.3.1/1005.3.2, and a Sprinkler System throughout (NFPA 13) genuinely reduces that per-occupant factor -- 0.2 in for stairs and 0.15 in for other egress components when sprinklered, versus a wider 0.3 in/0.2 in when not -- because sprinklers are credited with slowing fire growth and buying occupants more time to clear a wider bottleneck at a narrower width. The same sprinkler flag also widens Max Travel Distance for Business occupancies (200 ft unsprinklered to 300 ft sprinklered); other occupancy groups' real travel-distance allowances vary by table row in ways this simplified model does not fully separate, so treat that figure as most reliable for Business and only indicative elsewhere.

Width per Exit divides Total Stair Width evenly across the required exit count, floored at a 36-inch code minimum per exit door regardless of how that division comes out -- so a building with few occupants per exit still needs at least a 36-inch clear opening. Max Common Path of Egress Travel is the same sprinklered/unsprinklered flag applied to a shorter, stricter distance (100 ft sprinklered, 75 ft unsprinklered) than Max Travel Distance, reflecting that the single-direction "common path" before an occupant reaches a point with two remote exit options is held to a tighter limit than total travel to an exit. Number of Floors is shown for context but does not change any figure below -- these results are driven by occupant load alone, not building height. This is an educational illustration of how the pieces of an egress calculation fit together, not a code-compliance determination for an actual permit application.