IBC 1004.5 · Occupant load

How to use IBC Table 1004.5 occupant load factors

Occupant load drives exits, egress width, corridor ratings and restroom counts. Here is how to pick the right factor, gross vs net area, and a worked office example.

Need the actual table? Read IBC Table 1004.5 in the free ICC viewer →

How to calculate occupant load with Table 1004.5, step by step

Step	What you do	Watch out for
1	Break the floor plan into areas by function of space (office, assembly, storage, kitchen, etc.)	Use the function of each space, not the building’s overall occupancy group
2	Find each function in Table 1004.5 and note its factor (sq ft per occupant) and whether it is gross or net	The table marks every factor as gross or net — mixing them up is the most common error
3	Measure the area the factor calls for — gross or net	Gross = inside the exterior walls, including corridors, toilets, stairs and closets (vent shafts and courts excluded). Net = the used area only
4	Divide area by the factor for each space	Fixed seating (pews, bleachers, booths) is counted by seats, not by the table
5	Add the spaces to get the floor and building occupant loads	Where the code calls for rounding, round up — you cannot have a fraction of a person on an egress plan
6	Carry the number into exits, egress width, corridors and fixture counts	The AHJ can approve a higher (actual) number of occupants, and egress must then support it

Our own summary, not the code text. Read Table 1004.5 free at codes.iccsafe.org and verify against the IBC edition (2021, 2024 or local amendment) adopted by your AHJ.

Gross vs net floor area — what gets counted

Area	Gross	Net
Occupied rooms (offices, classrooms, sales floor)	Yes	Yes
Corridors, stairways, ramps	Yes	No
Toilet rooms	Yes	No
Mechanical / electrical rooms	Yes	No
Vent shafts and courts	No	No
Closets, wall thickness inside the exterior walls	Yes	No

Our own summary of the gross / net definitions in IBC Chapter 2. Check your edition for exact wording.

Worked example — 12,000 sq ft office floor

Input / step	Value	Source
Function of space	Business areas	Plans
Area measured	12,000 sq ft gross (includes corridors and restrooms)	Floor plan
Occupant load factor	150 sq ft per occupant, gross	Table 1004.5 (2018 IBC and later)
Occupant load	12,000 ÷ 150 = 80 occupants	Calculation
What it feeds	Number of exits, egress width, corridor rating, plumbing fixtures	Chapters 10 and 29

Worked example value only. Look up the full table in the free ICC viewer.

Common mistakes

Mistake	What to do instead
Using an old business factor from a pre-2018 code or an old drawing set	The business factor changed in the 2018 IBC — use the edition your AHJ enforces
Applying a net factor to gross area (or the reverse)	Check the gross / net designation in the table for every row
Calculating the whole building at one factor	Break out assembly, storage, kitchens and other functions separately
Forgetting that a tenant fit-out changes the number	A conference-room-heavy or call-center layout can raise the load — flag it before framing
Posting an assembly sign with a number nobody calculated	Use the approved occupant load from the life-safety plan

Our own summary, not the code text. Read Table 1004.5 free at codes.iccsafe.org and verify against the IBC edition (2021, 2024 or local amendment) adopted by your AHJ.

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The number every egress plan starts from

Read Table 1004.5 in the free ICC digital codes viewer. ICC offers free read-only access to the I-Codes. This page explains how to use the table in the 2021 and 2024 IBC; it does not reproduce it.

Table 1004.5 assigns a floor area per occupant to each function of space — assembly, business, educational, mercantile, storage and many more. Each factor is marked gross (measure everything inside the exterior walls) or net (measure only the used space). Divide the area by the factor and you have the design occupant load.

Worked example. A 12,000 sq ft office floor, measured gross, at the business factor of 150 sq ft per occupant, gives 80 occupants. That number sets how many exits the floor needs, how wide the stairs and doors must be, whether corridors must be rated, and how many toilets the building needs.

NFPA 101. Where a jurisdiction or owner (hospitals, schools, federal work) enforces the Life Safety Code, its Table 7.3.1.2 plays the same role. Read it in the free NFPA viewer.

Next steps: IBC egress requirements (single exit, travel distance, corridors) and live loads and minimum plumbing fixtures. This page is not a substitute for the design professional of record. Field PM keeps drawing revisions, RFIs and change orders on one job record, so a layout change that bumps the occupant load gets caught and priced.

FAQ

How do you calculate occupant load?+

Divide the floor area of each space by the occupant load factor for its function in IBC Table 1004.5, using gross or net area as the table specifies, then add the spaces together. Read the table free at codes.iccsafe.org.

What is the difference between gross and net floor area?+

Gross area is everything inside the exterior walls, including corridors, stairs, toilets, closets and mechanical rooms. Net area is only the space actually used, excluding those support spaces. Each factor in Table 1004.5 tells you which one to use.

What is the occupant load factor for an office?+

Since the 2018 IBC, business areas use 150 sq ft per occupant based on gross area (earlier editions used a denser factor). Concentrated business uses such as call centers can require a denser factor — check your edition.

Does NFPA 101 use the same factors?+

The NFPA 101 Life Safety Code has its own occupant load factor table, Table 7.3.1.2, organized by use rather than IBC occupancy group. Many factors line up with the IBC, but not all — where both codes are enforced, check both. NFPA 101 is free to read at https://www.nfpa.org/freeaccess.

Can the actual number of people exceed the calculated occupant load?+

Yes, with AHJ approval, but the means of egress then has to be designed for the higher number. The calculated load is a minimum design basis, not a cap on its own.

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