Gross floor area refers to the total area of the building within the exterior walls, with no deductions for hallways, closets, or other features. Net floor area refers to the actual occupied space, excluding non-occupiable areas like corridors, stairwells, restrooms, and mechanical rooms. Building codes specify whether to use 'gross' or 'net' for each occupancy type. Our calculator automatically indicates and applies the correct 'gross' or 'net' factor for your specific use.

Assembly occupant load factors vary significantly by use. For example, 'Assembly with fixed seats' uses the number of seats, while 'Assembly without fixed seats' varies: Concentrated use (e.g., chairs only) is typically 7 net sq ft/person, and Unconcentrated use (e.g., tables and chairs) is 15 net sq ft/person. Standing space is often 5 net sq ft/person. Our tool provides the exact factors for your state's code edition.

For mixed-use buildings, you must calculate the occupant load for each distinct area separately using its specific occupancy classification (e.g., Business for offices, Assembly for a lobby, Mercantile for retail). Then, sum these individual loads to determine the total building occupant load. Our calculator allows you to add multiple different areas to a single project worksheet to easily compute the aggregate load.

Occupant load requirements are dictated by the building code adopted by your specific state or local jurisdiction (e.g., IBC 2021, IBC 2024, California Building Code 2022, Florida Building Code 2023). Our calculator maintains an up-to-date database of state-specific code adoptions, automatically selecting the correct governing code basis for your selected jurisdiction to ensure compliance.

Office areas typically fall under 'Business' occupancy. The standard IBC factor is 150 gross sq ft per person. However, some states or specific code editions may have variations. To calculate, divide your office's gross square footage by 150 (or your state's specific factor). Our tool will confirm the exact factor for your location.

Educational occupancies usually have a load factor of 20 net sq ft per person for classrooms. Vocational shops or laboratories typically use 50 net sq ft per person. It is crucial to use 'net' area for these calculations. Our calculator provides these specific sub-categories to ensure you don't overestimate or underestimate the required egress capacity.

Retail stores (Mercantile occupancy) often use different factors for different floors. A typical baseline is 60 gross sq ft per person for sales areas on the ground floor and 300 gross sq ft per person for storage areas. Upper floors may use 60 sq ft as well. Our calculator breaks down these specific retail scenarios to help you apply the right factor.

Yes, the occupant load (or design occupant load) represents the maximum number of people—including employees, customers, visitors, and vendors—anticipated to be in the space at any one time. This total number dictates the requirements for means of egress (exits), plumbing fixtures, and fire protection systems.

Once you have the total occupant load, multiply it by the egress capacity factor (typically 0.3 inches per person for stairways and 0.2 inches per person for other egress components in the IBC). This gives you the minimum total required width for exits. Note: Egress calculations can be complex; our tool focuses on determining the accurate occupant load figure, which is the foundational first step.

Warehouses and storage areas generally have a low occupant load factor, typically 300 gross sq ft per person or sometimes 500 gross sq ft per person depending on the code edition and classification (S-1 or S-2). Because the density is low, the occupant load is often small relative to the floor area. Check our calculator for your state's current specific requirement.

Building codes are updated every 3 years (e.g., IBC 2018, 2021, 2024), and states adopt them on different schedules. Changes in code can alter load factors or area definitions (gross vs net). Using the wrong code edition can lead to permit rejection. Our Code Navigator integration ensures you are using the legally adopted code for your project's state and year.