Occupant load & egress worksheet

What an occupant load worksheet does

An occupant load worksheet estimates how many people a building or space is designed for by dividing each space's floor area by an occupant load factor (floor area per person). It then totals the spaces and multiplies the result by egress width factors to give the width that stairs and other exit components must provide.

This worksheet is deliberately code-neutral. You type in the factors from the code, edition and jurisdiction you are working under, such as the 2021 IBC's 150 ft² gross per person for business areas and 0.3 in per occupant for stairways, and it prints that source on every export. There is no built-in code table, so nothing is applied that you did not choose.

It rounds each space up to a whole person and reports total occupants, stair width and other egress width, with built-in 2021 IBC Table 1004.5 function-of-space presets you can override. Reference lines show the 2021 IBC minimum number of exits per storey and compare the widths with the component minimums, and the notes remind you about travel distance, but the worksheet does not check exit distribution, single-exit allowances, travel distance on the plan or compliance. For quick single-space checks, see the occupant load calculator and egress width calculator.

How to use the occupant load & egress worksheet

1. Choose Imperial or Metric. Areas are in ft² or m², load factors in ft² or m² per person, and width factors in inches or millimetres per person.
2. Enter the code, jurisdiction and edition your factors come from, for example "2021 IBC Table 1004.5 with local amendments". It is printed with the results and exports.
3. Enter the stair width factor and the other egress width factor per occupant from that source.
4. Add one row per space with its name and area. Pick a Function of space from the built-in 2021 IBC Table 1004.5 presets, which set the ft² per occupant and the gross or net basis, or leave Entered factor and type your own area per person and basis. Use Add space for more rows.
5. Read total occupants and the two widths, with a per-space table, the reference minimum number of exits per storey, the calculated widths against the 2021 IBC component minimums, and reminder notes on travel distance. Download the PDF worksheet or CSV, copy the results, or save your inputs to reopen later.

Worked example

Imperial: A 1,000 ft² space with a supplied 20 ft²/person factor gives 50 occupants. At 0.2 in/person, the width worksheet gives 10 in before any code minimums.

Metric: A 100 m² space with a supplied 2 m²/person factor gives 50 occupants. At 5 mm/person, the width worksheet gives 250 mm before any code minimums.

How to calculate occupant load

Occupant load = floor area ÷ occupant load factor. A 1,800 ft² dining room at 15 ft² net per person holds 120 people. Do this for every space, using the factor for that space's function, and add the results.

Net or gross matters. The IBC defines gross floor area as the area within the inside perimeter of the exterior walls, excluding vent shafts and courts, with no deduction for corridors, stairways, closets or interior walls. Net floor area is the actually occupied area, excluding accessory areas such as corridors, stairways, ramps, toilet rooms, mechanical rooms and closets. A factor marked "net" must be applied to net area, and a "gross" factor to gross area.

The worksheet rounds each space up to a whole person, a conservative convention. Check how your building official treats fractions, and note that the IBC counts spaces with fixed seating by the number of seats rather than by floor area.

IBC occupant load factors (Table 1004.5)

These examples from Table 1004.5 of the 2021 IBC show the kind of values the worksheet expects. They are not a preset. Use the full table from the edition adopted for your project, which has more categories and footnotes.

Two edition changes catch people out. The 2018 IBC raised the business factor from 100 to 150 ft² gross per person, and the 2021 IBC replaced the separate mercantile factors for basement and grade floors (30) and other floors (60) with a single 60 ft² gross. A 12,000 ft² office is 80 occupants at 150 but 120 at 100.

Egress width per occupant: the 0.3 and 0.2 inch factors

Once you have the occupant load, the required egress capacity is occupants × width factor. The 2021 IBC uses 0.3 in per occupant for stairways (1005.3.1) and 0.2 in per occupant for other egress components such as doors, corridors and ramps (1005.3.2). In most occupancies, buildings with an automatic sprinkler system throughout and an emergency voice/alarm communication system may use 0.2 in and 0.15 in instead. In metric, 0.3 in is 7.62 mm and 0.2 in is 5.08 mm.

Calculated width is rarely the whole answer. Code minimums often govern small loads: under the 2021 IBC, a stairway is generally at least 44 in wide (36 in where it serves fewer than 50 occupants, 1011.2) and egress doors need at least 32 in of clear width (1010.1.1). The larger of the calculated and minimum width applies. Where there is more than one exit, losing any one must not reduce the available capacity below 50% of the required capacity (1005.5). See egress and corridor widths for corridor minimums.

Worked example: occupant load for a small restaurant

A restaurant is entered with 2021 IBC factors, net areas for the dining and bar spaces and gross areas for the kitchen and storage. The worksheet rounds each row up and totals 184 occupants. At 0.3 in per person the stair width is 55.2 in; at 0.2 in per person the other egress components need 36.8 in in total.

With 184 occupants, an assembly space needs at least two exits under the IBC, and the 36.8 in has to be shared so that losing either exit still leaves at least half the required capacity. Each door also has to meet the 32 in minimum clear width, so the minimums, not the calculated width, are likely to set the door sizes here.

Who it is for and when to use it

Method, formulas & assumptions

Each space load is rounded up: ceil(area ÷ area per occupant), using your entered factor or a 2021 IBC Table 1004.5 function-of-space preset (ft² per occupant, gross or net basis). The width worksheet multiplies total occupants by the user-supplied stair and other-egress factors; reference lines compare them with 2021 IBC component minimums and list the minimum exits per storey from 2021 IBC 1006.3.

Imperial inputs are converted with exact factors (1 ft = 0.3048 m, 1 lb = 0.45359237 kg, 1 US gal = 3.785411784 L) before the calculation runs in SI, then results are converted back.

Common mistakes to avoid

• Applying a net factor to gross area, or the reverse. Net area excludes corridors, toilet rooms, stairs and mechanical rooms; gross area does not.
• Using an outdated factor. The IBC business factor changed from 100 to 150 ft² gross between the 2015 and 2018 editions.
• Using one factor for a whole floor with mixed uses. A dining room, bar and kitchen each have their own factor.
• Treating the width factor result as the final width. Minimum stair, corridor and door widths often exceed it for small loads.
• Counting spaces with fixed seats by floor area. Fixed seating is counted by seats (or bench length).
• Adding up exit widths without checking distribution. Capacity must survive the loss of any one exit.

Scope & limits

Supply the source, jurisdiction, edition, net/gross basis and factors. Reference values are informational: this worksheet does not check exit distribution, travel distance, occupancy-specific single-exit allowances or compliance. Existing resource pages remain unchanged.

Frequently asked questions

Further reading

• Occupant load calculator
• Egress width calculator
• Exit access travel distance calculator
• IBC occupancy classifications explained
• All drawing & geometry tools
• All free architecture & construction tools
• Harth resource library

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