This calculator estimates occupant load from floor area using a representative subset of IBC Table 1004.5, essentially unchanged across the 2018, 2021, and 2024 International Building Code. It is a reference estimate, not a code determination: confirm your jurisdiction’s adopted edition, the correct occupancy classification, and any local amendments with your local building department before relying on the result.
Before you use this: what this tool is and is not
This is a reference and estimating tool, not a code determination. It applies a representative subset of IBC Table 1004.5 to the numbers you enter. It does not know your project’s adopted code edition, occupancy classification, or any local amendment. Confirm the applicable edition and any local amendments with your Authority Having Jurisdiction (AHJ) before you rely on the result.
This page uses IBC Table 1004.5 as it appears in the 2021 and 2024 International Building Code; the table is essentially unchanged from the 2018 edition, and the 2024 edition added one new row, for information technology equipment facilities, which is not part of the subset below.
Calculate occupant load for one space
Occupant load calculator
Calculate one space or function at a time. For a mixed-occupancy building, repeat this for each distinct space and add the results — do not blend two uses into a single calculation.
The full IBC Table 1004.5 factors used here
Occupant load factors come from IBC Table 1004.5, Maximum Floor Area Allowances Per Occupant, cross-checked against door-hardware industry publisher iDigHardware’s coverage of the same table (both accessed 2026-09-17). This is a representative subset, not the complete table — follow the link above, or see the ICC’s own code library, for the full list of functions.
| Function of space | Factor | Net or gross |
|---|---|---|
| Assembly, unconcentrated (tables and chairs) | 15 sq ft per occupant | Net |
| Assembly, concentrated (chairs only, not fixed) | 7 sq ft per occupant | Net |
| Assembly, standing space | 5 sq ft per occupant | Net |
| Business areas | 150 sq ft per occupant | Gross |
| Mercantile | 60 sq ft per occupant | Gross |
| Educational classrooms | 20 sq ft per occupant | Net |
| Educational shops and vocational rooms | 50 sq ft per occupant | Net |
| Storage, general | 500 sq ft per occupant | Gross |
| Storage, stock and shipping areas | 300 sq ft per occupant | Gross |
| Residential | 200 sq ft per occupant | Gross |
| Institutional, inpatient treatment | 240 sq ft per occupant | Gross |
| Institutional, sleeping areas | 120 sq ft per occupant | Gross |
| Library reading rooms | 50 sq ft per occupant | Net |
| Library stacks | 100 sq ft per occupant | Gross |
| Day care | 35 sq ft per occupant | Net |
| Commercial kitchens | 200 sq ft per occupant | Gross |
| Exercise rooms | 50 sq ft per occupant | Gross |
Three ways this calculation is commonly misapplied
Mixed occupancy needs a separate calculation per space. A building with a restaurant, a retail floor, and offices has three different occupant loads to calculate, not one. Run this calculator once per distinct space or function, then add the results — never divide the whole building’s area by one blended factor.
"Concentrated" and "unconcentrated" assembly are easy to mix up. Unconcentrated assembly (15 net) is tables and chairs together, such as a restaurant. Concentrated assembly (7 net) is chairs only, not fixed to the floor, such as a lecture room set up with loose seating. The wrong choice roughly doubles or halves the calculated load.
Fixed seating is not calculated from area at all. A space with fixed seats or fixed benches — a theater or a stadium, for example — has its occupant load counted from the actual number of seats, not from floor area and a factor. This calculator does not compute that case; count the seats directly.
Where Groundbook fits
Groundbook’s document review already reads a project’s code analysis sheet and can compare a stated occupant load, occupancy classification, or exit requirement against the building code sources you upload for the review, flagging where the drawings and the code appear to disagree — see how Groundbook checks local building codes. It does not run this specific per-space calculation for you; use this tool to check the number, then have Groundbook check whether that number is consistent with the rest of the drawing set.