The required width of an exit door is governed by BC Section 1005. However, you must first calculate the occupant load of the space being served by the exit door. Then calculate the minimum width of the exit door by using the appropriate factor from Table 1005.1. (Hint: the exit door falls under the “other components” category)

##### OCCUPANT LOAD X 0.2 = EXIT DOOR WIDTH REQUIRED

For example, in a space that has an occupancy load of 400 people, the calculation would be 400x 0.2 = 80. Therefore, a minimum door width of 80 inches is required.

For spaces that require 2 exit doors, the required width represents the total width of the two doors.

Conversely, you can calculate the capacity of your door like this:

##### DOOR WIDTH / 0.2 = DOOR CAPACITY

For example, the exit capacity of a 36 inch door would be 36/0.2 = 180

### Read this to Avoid an Exit Door Capacity Mishap

“Multiple means of egress shall be sized such that the loss of any one means of egress shall not reduce the available capacity to less than 50 percent of the required capacity.”

- BC Section 1005.1

This means that if your occupant load is 400 and you require 2 exit doors, then each door must have a sufficient width to accommodate an occupant load of 200 (50% of 400). So each door must have a minimum width of 40 inches (200×0.2).

In other words, you couldn’t have one exit door that is 72 inches wide (two 36 inch doors) and another exit door that is 36 inches wide. It is true that the combined width of these doors is 108 inches (72+36), which is above the required 80 inches. However, this would not be acceptable because, if the 72 inch wide doors were “lost” (I’m guessing this means blocked off in a fire or something), this would reduce the required capacity by more than 50%. The capacity of the remaining 36 inch door would be 180 (36/0.2) which is less than 50% of 400.