Building Occupant Load from Area and Use (IBC Table 1004.5)
The one number the whole life-safety chain hangs on: the occupant load = sum over spaces of ceil(area / occupant-load factor). The factor is set by how the space is used, not its label - a 3,000 ft^2 office at 150 ft^2/occ is 20 people; the same floor as a standing bar at 5 ft^2/occ is 600. Bundled representative factors (business, assembly, mercantile, classroom, kitchen, industrial, storage, residential) are editable defaults; the factor and its net-vs-gross basis come from the AHJ-adopted code edition. A design aid, not a code-official determination.
Formula and source
per_space_load = ceil(area / olf); total_load = sum over spaces of per_space_load.
IBC 2021 §1004.5 and Table 1004.5 (occupant load = area / occupant-load factor, summed over spaces) and §1004.2 (round up to a whole person), by name.
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