Calculate Floor Area Ratio (F.A.R.)

How to Calculate Floor Area Ratio (FAR)

Understanding the Basics

Floor Area Ratio (FAR) is a critical metric in urban planning, calculated with the formula FAR = Gross Floor Area (GFA) / Total Lot Size. It is essential for determining the permissible size of a building on a particular lot, based on zoning laws.

Steps to Calculate FAR

To calculate FAR, measure the total gross floor area of the building, which encompasses all enclosed spaces within the external walls, and then divide by the total lot size. This calculation results in a decimal value representing the FAR, indicating how many times the lot area can be covered by the building area.

Requirements for Calculating FAR

Measurement Accuracy: Accurate measurements of the building's total gross floor area and the total size of the land lot are crucial. The land lot size can sometimes vary based on the shape of the property, hence needing precise measurement tools or techniques.

Factors Affecting FAR

FAR varies according to local zoning regulations, population growth patterns, and the nature of the land. Different zones such as industrial, residential, or commercial have specific FAR limits dictated by these factors.

Practical Example

For instance, a 20,000 sq. ft. commercial building on a 5,000 sq. ft. lot results in a FAR of 4.0 (20,000 / 5,000 = 4.0). This means the building's floor area is four times the size of its lot.

How to Calculate Floor Area Ratio (FAR)

Floor Area Ratio (FAR) is a critical tool used in the real estate and development industries to determine building size. Understanding how to compute FAR is essential for maximizing land use and complying with local zoning laws.

Step-by-Step FAR Calculation

To calculate the FAR, divide the Gross Floor Area (GFA) of the building by the size of the property lot. Use the formula: FAR = Gross Floor Area (GFA) / Total Lot Size. This calculation will yield a decimal value representing the FAR.

Understanding FAR Values

FAR is typically expressed in decimal format for clarity and precision. For example, a building with a GFA of 20,000 square feet situated on a 5,000 square foot lot results in a FAR of 4.0. Higher FAR values indicate a greater density of building area relative to the lot size.

Calculating Maximum Allowable Floor Area

To determine the potential development extent on a given lot, multiply the total lot size by the maximum FAR allowed under local zoning regulations: Maximum Allowable Floor Area = Total Lot Size x Max. Floor Area Ratio (FAR). This figure is crucial for developers planning new projects or expansions.

By applying these calculations, developers and real estate professionals can optimize land use, ensuring successful and compliant project developments.

Examples of Calculating Floor Area Ratio (FAR)

Example 1: Basic Calculation

To calculate FAR, divide the total floor area of all buildings on a lot by the size of the parcel of land. For instance, if a building has 10,000 square feet of floor area, and the lot size is 20,000 square feet, the FAR is FAR = 10,000 / 20,000 = 0.5.

Example 2: Multiple Buildings

When multiple buildings exist on a single lot, sum the total floor area of all buildings. If three buildings have floor areas of 5,000, 3,000, and 2,000 square feet, and the lot area remains 20,000 square feet, the combined FAR would be FAR = (5,000 + 3,000 + 2,000) / 20,000 = 0.5.

Example 3: Including Different Levels

In a multi-story building, include the floor area of each level. For a building with three floors each measuring 3,333 square feet, on a lot of 10,000 square feet, the FAR is FAR = (3,333 x 3) / 10,000 = 1.0.

Example 4: Adjustments for Unfinished Areas

Sometimes, areas such as basements or attics are not included in FAR calculations if they are not livable spaces. For example, if only 8,000 square feet of an 10,000 square foot building is livable, and the lot size is 5,000 square feet, calculate as: FAR = 8,000 / 5,000 = 1.6.

Example 5: Municipal Changes in FAR Limits

FAR varies by zoning laws which may dictate maximum allowable FARs. An area might change its zoning to promote higher density, increasing permissible FAR from 1.0 to 1.5. For a building with a previously maximum allowed building area of 10,000 square feet on a 10,000-square-foot lot, new regulations permit up to 15,000 square feet of building area, potentially leading to redevelopment or expansion projects.

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