Enter the average square footage of a floor and the number of floors of the building into the calculator to determine the gross floor area.

Gross Floor Area Formula

The following formula is used to calculate a gross floor area. 

GFA = A * F
  • Where GFA is the gross floor area (ft^2)
  • A is the average area of each floor in the building (ft^2)
  • F is the total number of floors in the building

To calculate the gross floor area, multiply the average area of each floor by the total number of floors in the build.

The area of each individual floor can further be calculated using the following formula:

A = L * W

Where L and W are the length and width of a square room. *This only works for floors with square layouts.

Gross Floor Area Definition

A gross floor area is defined as the sum of the areas of all floors in a building. A floor is typically limited to those with a ceiling height of at least 7.5 feet.

In general, any floors that meet the height requirement are included in the gross floor area. This includes garages, mezzanines, basements, etc.

Example Problem

How to calculate gross floor area?

First, determine the average area of each floor. In this example, the average area of the floors is found to be 1,000 ft^2.

Next, determine the total number of floors in the building. In this case, there are 40 floors in the entire building.

Finally, calculate the gross floor area using the formula above:

GFA = A * F

GFA = 1000 * 40

GFA = 40,000 ft^2