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The Floor Area Ratio (FAR) is the ratio of a building’s gross floor area to the total size of the land upon which it is constructed.

Floor Area Ratio( FAR) is a mathematical formula that determines how many square feet can be developed on a property in proportion to the plot area. The property area is multiplied by the FAR factor; with the result being the maximum floor area allowed for a structure on the lot. Local Zoning laws will assign a designated FAR based on the zoning section and structure use. The size of the structure will be directly impacted by the FAR assigned to the specific plot. The larger the FAR, the larger the structure can be. Understanding Floor Area Ratio is an essential demand for real estate development.

Understanding the basics of FAR will allow you to determine how numerous square feet can be developed on a property, or if there’s any room for expansion of a current structure on a lot. The FAR figures can also determine if there are available air rights to sell on the property. This composition is based on City Zoning but the generalities can apply beyond any areas that use FAR as a metric for development regulations.

FAR Calculation Example

Plot Width = 30 Feet

Plot Length = 100 Feet

Plot Area = 30’ x 100’ = 3,000 Square Feet

Allocated FAR = 4.0

FAR x Plot Area = Maximum Buildable Area

4.0 x 3,000 SF = 12,000 SF

This property can be developed with a 12,000 square foot building. This is called the Zoning Floor Area.


The regional zoning laws will identify what the FAR ( Floor Area Ratio) is for your zoning district. Depending on the district, specific property conditions, and proposed constructing use. In different cases, these may be easier or more complicated to figure out. For instance, a mixed-use structure may have a different FAR for each use.

Once you have your maximum structure area. You can now get an idea of how large of a design you can put onto a lot. You can also subtract the size of the current structure on a lot to see how important an expansion is allowed.

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