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In order to apply the model code requirements correctly, it is sometimes necessary to calculate the amount of egress width required or provided by the door openings serving the space.  For example, if a restaurant has an occupant load of 300 people, how many doors are needed, and what is the required egress width provided those doors?

The Egress Capacity Estimator below can help you to estimate the total amount of clear opening width that must be provided by the doors in the means of egress.  It can also estimate how many building occupants can be accommodated by the existing or planned door width.  Here are a few things to consider when using the estimator:

  • Adopted Code:  The factors used in this estimator were taken from the 2024 edition of the I-Codes and the NFPA codes.  Refer to the adopted code in the project’s jurisdiction to check for variations.
  • Number of Exits:
    • For rooms or spaces with a low occupant load, one exit may be acceptable. For example, Table 1006.2.1 in the 2024 edition of the IBC allows a single exit for assembly, business, educational, factory and industrial, mercantile, and utility occupancies with an occupant load of 49 or less, if the common path of travel is within a certain length.
    • For larger spaces in these use groups with an occupant load of more than 49, a second exit would be required.
    • For spaces with a high occupant load, the IBC requires additional exits – a minimum of 3 exits for any space with an occupant load of 501 to 1,000, and 4 exits if the occupant load is more than 1,000.
    • Consult the code for information specific to your project, as there are several exceptions to these requirements.
  • Calculation:  In recent editions of the IBC, Section 1005 covers Means of Egress Sizing, including sizing for stairways and “other egress components” – doors, gates, corridors, aisles, and ramps. The required egress width for these “other” components of an egress route is calculated by multiplying the occupant load served, by the egress capacity factor (note that stairways have a different egress capacity factor).  The method used by NFPA 101 is the same, but the egress capacity factors vary slightly from those of the I-Codes.
  • Clear Width:  The clear opening width of a door is measured from the face of the door with the door open 90 degrees, to the stop on the strike jamb of the frame. For pairs of doors, the clear width of the active leaf is measured from the face of the door to the removable mullion or to the edge of the inactive leaf in the closed position. To calculate the egress width of the entire opening for a pair without a mullion, measure between the faces of both doors when open to 90 degrees.
  • Minimum Width:  Although the estimator might show a required clear width of less than 32 inches based on the calculation (ex. 100 occupants * 0.2 inches per occupant = 20 inches), the minimum clear width of a door in a means of egress is 32 inches, or as required by the adopted code.
  • Decoded: Calculating the Egress Width of Door Openings: For more information about how to calculate the egress width, including examples, refer to this Decoded article.

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Option A: Calculate the required egress door width based on the occupant load.

Step 1: Choose from the following occupancy types in the applicable model code.
Note: If the required egress width shown is less than 32 inches, the minimum clear width will be 32 inches each for the quantity of doors required by code.

Option B: Calculate the occupant load that can be accommodated by the available doors.

Step 2: Choose from the following occupancy types in the applicable model code.

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The actual code publications should be consulted when comprehensive data is required and to ensure compliance with the applicable codes.  Accordingly, Allegion and its related companies, subsidiaries, sectors, divisions, and affiliates, and their respective officers, directors, employees, attorneys, agents, successors, and assigns (hereinafter referred to as “Allegion”) make no representations or warranties, express or implied, with respect to the information contained in this resource or output of the estimators, nor does it assume any obligation or liability for any advice provided herein or any reliance upon the estimators by others.