Occupancy load is the maximum permitted number of people in a building or space, calculated by dividing the floor area by the per-occupant area factor specified in IBC Table 1004.5. Office space is calculated at 100 square feet gross per occupant. Assembly spaces with concentrated seating use 7 net square feet per occupant. Restaurant dining rooms are 15 net per occupant. Retail is 60 gross per occupant. The calculated occupancy load drives required egress capacity, exit count, plumbing fixture count, and the posted occupancy signs visible in commercial spaces.
Occupancy load is enforced through plan review, posted signs, and fire marshal inspection. Exceeding the posted occupancy is an enforcement violation that can shut down the business. Overstating occupancy at design (to support a larger restaurant or assembly venue) increases egress and fixture requirements and therefore cost. Understating it caps the legal maximum and limits the owner's revenue capacity. Get the calculation right early in design.