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Floor Area Ratio (FAR)

Step-by-Step Guide to Understanding the Floor Area Ratio (FAR)

Last Updated February 20, 2024

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Floor Area Ratio (FAR)

How to Calculate Floor Area Ratio (FAR)

The floor area ratio, often abbreviated as “FAR”, compares a building’s size and the land on which the property was built.

Therefore, the floor area ratio (FAR) is the ratio between the gross floor area (GFA) of a building and the total lot size.

The practical use-case of the FAR by real estate property developers is to determine the maximum square footage of a building that could potentially be developed on a specific parcel of land.

The two components in the floor area ratio (FAR) metric are the gross floor area (GFA) and the total lot size.

  1. Gross Floor Area (GFA) → The total square footage (sq. ft.) measured between the external surfaces of the exterior, enclosing walls of a building.
  2. Total Lot Size → The size of the piece of land on which the property is situated. The shape of the property determines the ease at which the lot size can be measured. For properties constructed in the shape of a square or more commonly, rectangularly, sizing the property is much easier.
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Zoning Laws and Regulations

The zoning laws of a specific area serve as constraints on the floor area ratio (FAR), which is a factor that developers must be cognizant of amid the planning process.

Zoning regulations apply to land and properties, both commercial and residential, to establish boundaries between different property types.

On that note, commercial property developers are obligated to submit formal zoning reports to institutional lenders before obtaining approval for financing for a commercial loan.

Otherwise, there could be penalties for monetary fines and legal risks for breaching compliance regulations, which can negatively impact returns on a property development project.

Floor Area Ratio Formula (FAR)

The floor area ratio (FAR) is calculated by dividing the gross floor area (CFA) of a building by the total lot size.

Floor Area Ratio (FAR) = Gross Floor Area (GFA) ÷ Total Lot Size

The FAR is usually expressed in decimal notation, rather than percentage form.

For example, suppose a commercial building with 20k square feet (sq. ft.) is located on a 5k square foot lot.

The floor area ratio (FAR) of the commercial building is 4.0x, which we determined by dividing the gross floor area (GFA) by the total lot size.

  • Floor Area Ratio (FAR) = 24,000 ÷ 6,000 = 4.0x

However, real estate development firms (or “property developers”) often derive the maximum allowable floor area based on the specific floor area ratio (FAR) of a zoning district.

The maximum allowable floor area can be calculated by multiplying the size of the zoning lot by the maximum FAR.

Maximum Allowable Floor Area = Total Lot Size × Max. Floor Area Ratio (FAR)

Therefore, the maximum size of the building that can be developed on a given lot size, or land parcel, can be determined in units of square footage.

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What is a Good Floor Area Ratio (FAR)?

The higher the floor area ratio (FAR) of a given property, the greater the density of the developmental project.

In commercial real estate (CRE), the floor area ratio (FAR) directly impacts property value, particularly in urban areas.

Broadly put, a higher floor area ratio (FAR) implies more potential revenue that can be generated post-development, since there is more leasing space in square feet.

  • Higher Floor Area Ratio (FAR) → More Expensive Land and Higher Property Value
  • Lower Floor Area Ratio (FAR) → Less Expensive Land and Lower Property Value

Therefore, in property development, land located in zones with a higher maximum floor area ratio (FAR) tends to be priced at higher rates

High-density urban areas, such as New York City (NYC), have much higher maximum floor area ratios.

In effect, real estate property developers can construct buildings with more leasable space, resulting in greater potential “upside” in profits.

To illustrate the concept, a real estate building with a floor area ratio (FAR) of 5.0x on a 10k square foot lot permits 25.0% more leasable space (50k maximum square feet) than if its FAR were 4.0x instead (40k maximum square feet).

Floor Area Ratio Caveats (FAR)

The statement that a higher floor area ratio (FAR) warrants higher pricing is a generalization, rather than a rigid rule.

  • Obstructed View → If the views from a property are obstructed from the high-density area, that trait could reduce the value of the property.
  • Higher Construction Costs → The higher revenue potential of the building post-development coincides with higher construction costs and a prolonged development period, meaning the time (and monetary) commitment is greater given the longer timeframe.

Floor Area Ratio Calculator (FAR)

We’ll now move to a modeling exercise, which you can access by filling out the form below.

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Floor Area Ratio Calculation Example (FAR)

Suppose we’re tasked with calculating the floor area ratio (FAR) of a commercial building in New York City (NYC).

The building is situated in the NYC C4-7 districts, and is mapped in densely-built parts of Manhattan, where the maximum floor area ratio (FAR) is 10.0x for commercial properties.

  • Maximum Floor Area Ratio (FAR) = 10.0x

NYC Floor Area Ratio Example (FAR)

The gross floor area of the commercial building is 12k square feet (sq. ft.), while the total lot size is 1.4k square feet (sq. ft.).

  • Gross Floor Area (GFA) = 12,000 sq. ft.
  • Total Lot Size = 1,400 sq. ft.

The floor area ratio (FAR) is 8.6x, which we determined by dividing the gross floor area (GFA) by the total lot size.

  • Floor Area Ratio (FAR) = 12,000 sq. ft. ÷ 1,400 sq. ft. = 8.6x

Since the maximum floor area ratio of 10.0x exceeds the 8.6x floor area ratio (FAR) of the commercial building, the property is in compliance with NYC zoning regulations.

Floor Area Ratio Calculator (FAR)

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