Occupant Load Factors by Occupancy Type (IBC Table 1004.5)

How the factor works

Occupant load = floor area ÷ occupant load factor. The factor is a density assumption: how many square feet the code presumes each person occupies in that function. A low factor means a dense space (lots of people); a high factor means a sparse one. (For how the resulting load drives exits and egress width, see our occupant load guide and means of egress guide.)

Function, not just occupancy classification

The most important rule in applying Table 1004.5: use the function of the space, not merely the building's occupancy classification. A business-classified building can contain a conference room used for assembly, a storage room, and a break-room kitchen — each takes its own factor based on what it's used for, not the building's overall Group B label. Applying one blanket factor across mixed functions is a common source of error.

Gross vs. net area

The other make-or-break distinction:

• Gross area — the total floor area within exterior walls, including corridors, columns, restrooms, and mechanical spaces. Used for factors marked "gross" (e.g., business, mercantile, storage).
• Net area — the actual occupiable space only, excluding walls, columns, accessory areas, and corridors. Used for factors marked "net" (e.g., assembly, classrooms).

Table 1004.5 specifies which basis applies to each function. Using gross where net is required (or vice versa) changes the result — a classroom computed on gross area yields a higher occupant load than the net basis the code intends.

Common factors (IBC Table 1004.5, selected)

These are common rows, not the full table — confirm the exact value for your function in Table 1004.5 of the edition your jurisdiction has adopted. (Concentrated business uses such as call centers can carry a denser factor under provisions added in the 2018 and later editions.)

A worked example

A 3,000 sq ft restaurant dining area with tables and chairs: 3,000 ÷ 15 = 200 occupants (assembly, unconcentrated, net). At 200 occupants, the space needs two exits, doors swinging in the direction of egress, and egress width sized to that load. Re-run that same area at a business factor of 150 and you get 20 occupants — a tenfold error that would understate every egress requirement. The factor selection is the design.

Common mistakes

• Classification instead of function — applying the building's Group label to a room whose actual use takes a different factor.
• Gross/net mix-up — using total floor area where net occupiable area is required, inflating or deflating the count.
• Stale factor — using a value from a different edition; while most factors are stable, some change between editions and your AHJ's adopted edition governs.
• Ignoring the minimum — the code allows the actual (higher) occupant load to control, but the table value is a floor you can't go under for that function.