Floor area ratio (FAR) is a zoning measure that compares the total floor area of a building with the area of the lot it sits on. Cities use a maximum FAR to control how dense a neighborhood can become. For owners and investors, it answers a simple question: how much building does the zoning allow on this land?
How to calculate it
FAR = Total gross floor area of all floors / Lot area
To find the most floor area allowed, rearrange it:
Maximum floor area = Lot area x Maximum FAR
Gross floor area usually means the area of each floor measured to the outside walls, added up across floors. What is included or excluded, such as basements, attics, garages or balconies, depends on the local code.
Worked examples
An existing building. A hypothetical two story fourplex has 2,400 square feet on each floor, or 4,800 square feet in total, on a 6,000 square foot lot. Its FAR is 4,800 divided by 6,000, or 0.8.
Room to expand. If that lot is zoned for a maximum FAR of 1.2, the most floor area allowed is 6,000 x 1.2, or 7,200 square feet. That leaves 2,400 square feet of unused allowance, enough in principle for a third floor of the same size. Height limits, setbacks, parking rules and building codes still have to allow it.
Comparing lots. A 5,000 square foot lot with a FAR of 3.0 allows 15,000 square feet. A 10,000 square foot lot with a FAR of 1.0 allows 10,000 square feet. The smaller lot can hold more building.
FAR vs other zoning limits
FAR rarely works alone. Most zones also set:
- Height limits, in feet or stories
- Setbacks from the front, side and rear lot lines
- Lot coverage, the share of the lot the building footprint may cover
- Density limits, such as units per acre
- Parking minimums, in places that still require them
The tightest of these rules is the one that actually limits a project.
Why it matters for landlords
FAR helps you judge a property’s potential before you buy. A building well below the allowed FAR may have room for an addition or extra units, which can add value; one at or above the limit, perhaps built before current rules, may have no room to grow and may face limits if it is ever rebuilt. Before planning any expansion, confirm the zoning with the planning office and talk to an architect. After you add units, update the certificate of occupancy, your insurance and your unit list so leases and rent are tracked for every new home.
Related terms
Related questions.
Does a FAR of 2.0 mean a two story building?
Not necessarily. It means total floor area can be twice the lot area. That could be two stories covering the whole lot, four stories covering half of it, or another mix, as long as setback and height rules also allow it.
Do basements and parking count toward FAR?
It depends on the local code. Many codes exclude below grade space, parking or mechanical rooms, while others count them. Always check the definitions section of the zoning ordinance.
Where do I find the FAR for a property?
In the local zoning map and ordinance, usually online from the city or county planning department. The planning office can confirm the zone and any overlays.