Understanding Floor Area Ratio (FAR)
Floor Area Ratio (FAR) measures the relationship between a building’s usable floor area and the size of the lot it occupies. Municipalities use FAR in zoning to control building density, guide urban form, and influence property values and development potential.
Formula and how to calculate it
FAR = Total building floor area ÷ Gross lot area
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- Total building floor area: sum of all usable floors.
- Gross lot area: total lot surface area.
- Many jurisdictions exclude unoccupied spaces (for example: parking garages, stair and elevator shafts, and some basements) when calculating usable floor area; check local zoning rules.
What FAR tells you
- Density: Higher FAR allows more floor area per lot, enabling taller or more massive buildings. Lower FAR restricts development intensity.
- Flexibility: Different building configurations (e.g., single-story footprint vs. multi-story building) can produce the same FAR.
- Planning control: FAR is a primary tool for municipalities to manage population density, infrastructure load, and neighborhood character.
- Economic impact: Increasing allowable FAR can enable more units or leasable space, potentially lowering per-unit costs and increasing supply.
Examples
- A 1,000 sq ft building on a 4,000 sq ft lot: FAR = 1,000 ÷ 4,000 = 0.25.
- The same lot with a two-story building of 500 sq ft per floor: total floor area = 1,000 sq ft → same FAR = 0.25.
- If a lot has FAR 2.0 and the lot area is 1,000 sq ft, the maximum total floor area allowed = 2,000 sq ft (e.g., two 1,000 sq ft floors).
- Real-world example: An apartment complex of 17,350 sq ft sitting on a 1.81-acre lot (78,843 sq ft) has FAR ≈ 17,350 ÷ 78,843 = 0.22.
Common questions
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What is “bulk” in zoning?
Bulk refers to the overall size and shape of buildings on a lot and related features (setbacks, height, and FAR are examples of bulk controls). -
How does FAR differ from lot coverage?
FAR measures total floor area relative to lot size. Lot coverage measures the portion of the lot covered by buildings and structures (including garages, sheds, and other surface structures). Lot coverage relates to ground-level footprint, while FAR captures total floor space across stories. -
How does FAR relate to supply and demand?
FAR limits the amount of new housing or commercial space that can be developed on available land. Increasing FAR can raise supply, which affects market prices and availability; conversely, restrictive FAR can constrain supply and support higher land or unit prices.
Conclusion
FAR is a foundational zoning metric that shapes urban density, development capacity, and property value. Understanding local FAR rules helps developers, planners, and property owners evaluate what can be built on a site and how changes in FAR affect housing and commercial supply, neighborhood character, and infrastructure demands.