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Building Occupant Load from Area and Use (IBC Table 1004.4)
The one number the whole life-safety chain hangs on.
Example
You enter
- Spaces area 3000, olf 150; area 600, olf 15
You get
- Total occupant load 60 occupants
- Space count 2
Checked against published worked examples from: International Code Council.
Details, formula, and sources
ScopeThe 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 or tableper_space_load = ceil(area / olf); total_load = sum over spaces of per_space_load.
Source and editionIBC 2027 §1004.4 and Table 1004.4 [§1004.5 and Table 1004.5 in IBC 2021] (occupant load = area / occupant-load factor, summed over spaces) by name; each space is rounded up to a whole person as conservative practice (§1004.2 covers cumulative loads and states no rounding rule).
Free accessThe occupant-load relation is stated in the published IBC 2027 §1004.4 [1004.5 in IBC 2021]; the arithmetic is public. The occupant-load factors are the IBC 2027 Table 1004.4 values (Table 1004.5 in 2021; the business 150 gross and unconcentrated assembly 15 net factors are unchanged) for the actual use.
What governsEstimate. AHJ and licensed professional govern.
API field namesspaces, total_load, space_count
- Per-space load ceil(area / occupant-load factor): each space rounded up to a whole person (conservative practice)IBC 2027 §1004.4 [1004.5 in IBC 2021]
- Total the occupant load is the sum across spaces; the use, not the area alone, governs the factorIBC 2027 Table 1004.4 [Table 1004.5 in IBC 2021]
- Factor source the bundled factors are representative defaults; the AHJ-adopted edition and the actual use set the governing factor and its net-vs-gross basisIBC 2027 Table 1004.4 [Table 1004.5 in IBC 2021]