Floor area ratio (FAR)
The Floor Area Ratio (FAR) is the ratio of a building’s total floor area (zoning floor area) to the size of the piece of land upon which it is built. FAR is a key zoning metric used in urban planning and real estate development to regulate building density and ensure sustainable growth.
How to Calculate the Floor Area Ratio (FAR)
To calculate the Floor Area Ratio (FAR), divide the Gross Floor Area by the Buildable Land Area. The result is the Floor Area Ratio (FAR).
FAR = Gross Floor Area (G) ÷ Buildable Land Area (B)
Step-by-Step Calculation
STEP 1: Determine the Total Buildable Land Area
Calculate the buildable land area in square feet for the site. The buildable land area is that portion of a development site where construction can legally and reasonably occur – excluding public streets and rights-of-way, wetlands and watercourses, and other constraints.
Formula:
Buildable Land Area (B) = (Parcel Width × Parcel Depth) – Square feet of undevelopable land (if applicable)
STEP 2: Determine the Floor Area of Each Story
Calculate the area of each story (floor) of the building, typically measured between the exterior walls. Those portions of each story above the ground surface prior to any manipulation or grading are usually included in the calculation.
Note: This includes the full footprint of each level, accounting for architectural features like overhangs or balconies where specified by local zoning codes.
STEP 3: Determine the Gross Floor Area of the Building
Gross floor area is the sum of the floor area of each story. This represents the total zoning floor area across all levels.
Formula:
Gross Floor Area (G) = Floor Area of 1st Story + Floor Area of 2nd Story + ... (for all floors above the ground)
Why FAR Matters in Real Estate Development
FAR helps cities control urban density, preserve open space, and promote efficient land use. A higher FAR allows for taller or larger buildings on a given lot, while a lower FAR encourages low-density development. Always check local zoning ordinances, as FAR calculations can vary by jurisdiction (e.g., inclusions/exclusions for basements, mezzanines, or parking).
Practical Tip: Use site plans, surveys, and architectural drawings to ensure accuracy. Tools like AutoCAD or GIS software can assist in precise measurements. Consult a local planner or architect for jurisdiction-specific rules.
Mastering FAR calculations empowers developers, architects, and investors to maximize project potential while complying with zoning regulations.