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Calculating Occupancy Loads for Safe Start

Tuesday, June 9, 2020   (0 Comments)
Posted by: Christine Miclat
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 Calculating Occupancy Loads for Safe Start

BOMA has been in contact with the Fire Marshals in Seattle and Bellevue to ask about how to calculate Occupancy Loads for the recently approved Safe Start Phase 1.5 in King County that allows professional and personal services to re-occupy office space at 25% of capacity.


The information below may be updated by the departments, however, this information should help you determine the approximate occupancy numbers with your tenant businesses.


Seattle - Calculating Occupancy Loads for Safe Start

Fire Code and Fire Safety Documents

Here are a few of the most common occupant load factors, based on use, that may be helpful references as you calculate reduced occupancy loads under the Safe Start guidelines:


  1. For assembly areas that do not have fixed seating but have tables and chairs in use (such as a restaurant or conference room) the ratio is 1 person per 15 square feet of space.
  2. For assembly areas that do not have fixed seating but have chairs only in the room (more concentrated use) the ratio is 1 person per 7 square feet of space.
  3. For assembly areas that are for standing room only (waiting areas) the ratio is 1 person per 5 square feet of space.
  4. Business occupancies (offices) have ratios of 1 person per 130 square feet in fire sprinklered buildings and 1 person per 100 square feet in non-fire sprinklered buildings.
  5. Mercantile (stores) have a ratio of 1 person per 60 square feet.
  6. Residential areas are usually 1 person per 200 square feet, but that number can differ based on the type of residential buildings.

These numbers are from the City of Seattle Building and Fire Code and are slightly different than the State Code.  For more specific approvals on occupant load, please contact the Seattle Department of Construction and Inspections, the City agency responsible for determining occupancy and occupant loads


Bellevue - Calculating Occupancy Loads for Safe Start

Published restaurants and retail businesses in this document also helps calculate office space occupancy. Below is a copied section.


Office: 100 s.f./person

Example: Office area of 20,000 s.f. (not including conference rooms, storage rooms or restrooms): 20,000/100 = 200 persons.

Phase 1.5 Re-Opening: Maximum 25% capacity. In this example, the maximum occupancy would be 50. Building and Fire Codes are used to determine the occupant load (capacity) of buildings and spaces. The determination is used to ensure that there are enough exits, they are properly separated, and of sufficient width so that in an emergency occupants can safely evacuate. The reduced occupant load required by the Governor’s Phased reopening reduces the normally allowable occupant load to help maintain proper social distancing.

Additional Help? An online occupant load estimator is available at this site: fireinspection360.com/occupantload

You can also contact Fire Prevention staff fire_prevention@bellevuewa.gov or 425-452-6872 for additional assistance as well.


Bellevue Fire will be developing an update to reflect the professional office calculations. The link below is an online occupancy calculator.

Select the link, choose “business areas”, plug in your square footage and select the 25% occupant load and you’ll have the answer.  Caveat – don’t include storage rooms & restrooms in that area.


Access the Occupant Load Calculator here.

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