Occupant load calculator: IBC 2021 Table 1004.5 and egress width
List your spaces by function and area to get the design occupant load, the required stairway and door capacity, the minimum number of exits and whether one exit is enough. Check your stairs next with our stair calculator.
Every Table 1004.5 factorFixed seats, benches and boothsEgress width per §1005.3Exits per Table 1006.3.3ft² or m²
Building
Used for the single-exit check (Table 1006.2.1) and because Groups H and I-2 cannot use the reduced egress factors.
Both together lower the egress factors to 0.2" (stairways) and 0.15" (other components) per occupant.
From the most remote point to where occupants have a choice of two exits. Checks whether one exit is enough.
Spaces
Add one row per function of space. Each row is rounded up to whole occupants, then added up.
Occupant load and egress
Enter the area of at least one space.
Design occupant load
–
| Space | Function | Factor | Quantity | Occupants |
|---|
Egress requirements (IBC 2021)
Covers Table 1004.5, §1004.6, §1005.3, §1006, §1010.1.1, §1011.2 and Table 1020.3 of the 2021 International Building Code only. Exit access travel distance, assembly aisles (§1029), cumulative loads through intervening rooms (§1004.2) and the story single-exit tables 1006.3.4 are not checked.
Local codes differ: the Egyptian fire code, Saudi SBC 801, the UAE Fire and Life Safety Code and local IBC amendments use their own factors and limits. Check against the code that applies and have the design verified by a qualified professional.
Need the egress plan modelled? We build Revit models and families for your project, from code plans to construction documents.
Request a custom Revit projectWork out occupant load and egress in three steps
Describe the building
Pick the occupancy group and tick whether it is sprinklered throughout and has an emergency voice/alarm system. Both change the egress factors.
Add your spaces
Add a row per function of space with its gross or net area, or the number of fixed seats, bench length or booth length. Areas can be in ft² or m².
Read the egress results
You get the occupant load per row and in total, the stairway and door capacity in inches and millimetres, minimum widths, the number of exits and a single-exit check.
How to calculate occupant load and egress width
For each space, divide the floor area by the occupant load factor from IBC 2021 Table 1004.5 and round up to whole people. Add the spaces together for the design occupant load.
Stairway capacity = occupants × 0.3″ (0.2″ sprinklered + voice/alarm)
Other components = occupants × 0.2″ (0.15″ sprinklered + voice/alarm)
Worked example: a 5,000 ft² banquet hall with tables and chairs is unconcentrated assembly at 15 ft² net, so 5,000 ÷ 15 = 333.3, rounded up to 334 occupants. Its stairways need 334 × 0.3 = 100.2″ of capacity and its doors 334 × 0.2 = 66.8″. With 334 occupants it needs at least 2 exits.
Each stairway must still be at least 44″ wide (36″ under 50 occupants, §1011.2) and each door 32″ clear (§1010.1.1), whichever is greater.
The IBC says the occupant load shall be not less than area ÷ factor, which is why fractions round up. Rounding each space before adding is the conservative way to do it.
Common IBC 2021 occupant load factors
| Function of space | ft² per occupant |
|---|---|
| Assembly, concentrated (chairs only) | 7 net |
| Assembly, standing space | 5 net |
| Assembly, unconcentrated (tables and chairs) | 15 net |
| Business areas | 150 gross |
| Concentrated business use (§1004.8) | 50 gross |
| Educational classroom | 20 net |
| Exercise rooms | 50 gross |
| Kitchens, commercial | 200 gross |
| Mercantile | 60 gross |
| Residential | 200 gross |
| Accessory storage, mechanical rooms | 300 gross |
| Warehouses | 500 gross |
| Occupant load | Minimum exits (Table 1006.3.3) |
|---|---|
| 1–500 | 2 |
| 501–1,000 | 3 |
| More than 1,000 | 4 |
Spaces under the Table 1006.2.1 limits, for example a Group B space of 49 or fewer with a short common path, may have a single exit. This page follows IBC 2021 only. The Egyptian fire code, Saudi SBC 801 and the UAE Fire Code use their own values.
Occupant load questions
Divide the floor area of each space by its occupant load factor from IBC Table 1004.5, round up, and add the spaces. A 1,000 ft² office at 150 ft² gross per person gives 6.67, so 7 occupants. Fixed seating counts one person per seat, or one per 18″ of bench.
Gross area is everything inside the exterior walls, less shafts and courts, and includes corridors, stairs, toilets and walls. Net area is only the space actually used for the activity, so it excludes corridors, stairs, toilets, mechanical rooms and closets. Table 1004.5 says which one each factor uses.
Business areas use 150 ft² gross per occupant under IBC 2021. Call centres, trading floors and similar dense business areas use the concentrated business factor of 50 ft² gross (§1004.8), and conference rooms are often counted as unconcentrated assembly at 15 ft² net.
Multiply the occupant load by 0.3″ for stairways and 0.2″ for doors, corridors and ramps (IBC §1005.3). In buildings sprinklered throughout with an emergency voice/alarm system, other than Groups H and I-2, the factors drop to 0.2″ and 0.15″. The result can never be less than the component minimums, such as 44″ stairs and 32″ clear doors.
Table 1006.3.3 requires 2 exits for 1–500 occupants per story, 3 for 501–1,000 and 4 for more than 1,000. A single exit is allowed only where the occupant load and common path of travel are within Table 1006.2.1, for example 49 occupants and 75–100 ft in a Group B space.
Up. The IBC says the occupant load shall be not less than the area divided by the factor, so 6.67 becomes 7 people. Rounding each space up before adding the spaces is the conservative approach and the one this calculator uses.
Need a custom tool, Dynamo script or Revit family?
Tell us about your project and we will send you a quote before any work starts.