What Is Floor Area Ratio? A NYC Buyer’s Guide to FAR
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Floor area ratio, or FAR, is a building’s total floor area divided by its lot size. A FAR of 2.0 means the floor area can run up to twice the lot size. In New York City, zoning sets the maximum FAR for every lot, from about 0.5 in low-density areas to 10 or more in dense Manhattan.
FAR is a niche number that only matters if you’re buying a townhouse, a small building, or anything you might want to expand. When it matters, it matters a lot, so here’s the plain version.
What is floor area ratio?
FAR is a rule about how much building the city will let you stack on a plot of dirt. Take the building’s total floor area and divide it by the lot area. A 4,000-square-foot building on a 2,000-square-foot lot has a FAR of 2.
Every lot in New York City sits in a zoning district, and each district has a maximum FAR. A low-density residential district might allow a FAR of 0.5; a dense Manhattan district might allow 10 or more.
The Department of City Planning’s ZoLa map shows the district for any address. Our buying process guide covers the rest of the due diligence that this fits into.
How to calculate floor area ratio
The floor area ratio calculation is simple. Divide, then apologize to whoever thought the attic was free square footage, because “floor area” has a precise zoning definition that isn’t the square footage your broker listed.
- Total floor area: the sum of the enclosed floor space on every story, with some exclusions like cellars below grade, mechanical space and, in some districts, a portion of the ground floor.
- Lot area: the size of the zoning lot, from the survey or public records.
- Divide the floor area by the lot area to get the FAR.
If the building’s floor area is 3,000 square feet and the lot is 2,000 square feet, the FAR is 1.5. If the district allows 2.0, then 0.5 of the FAR is unbuilt.
| Example | Floor area | Lot area | FAR |
|---|---|---|---|
| A townhouse at its limit | 4,000 sq ft | 2,000 sq ft | 2.0 |
| The same lot, under-built | 3,000 sq ft | 2,000 sq ft | 1.5 (0.5 unused) |
Unused floor area ratio
Unused FAR is the invisible extension you may or may not be paying for. It’s the gap between what’s built and what the zoning allows. A townhouse built to a FAR of 1.5 in a district that permits 2.0 has room, on paper, for an additional 500 square feet per 1,000 square feet of lot area.
Whether you can actually use it is a separate question. Height limits, the sky exposure plane, rear-yard rules, and landmark status can all block an addition even when the FAR math says yes. And a landmarked building, or one in a historic district, needs Landmarks Preservation Commission approval for any exterior changes. Before you pay a premium for “expansion potential,” have an architect confirm the addition is buildable.
FAR bonus in NYC
New York sometimes lets a building exceed the base FAR. The city trades extra floors for things it wants and rarely for the reasons you’d guess. A community facility, such as a school or medical office, can have a higher FAR than residential space in the same district. Inclusionary housing programs grant bonus FAR to developments that include permanently affordable units.
For a buyer of an existing home, this is mostly background, but it explains why a building next door might be taller than the zoning “allows,” and why a development site trades on more than its base FAR.
Floor area ratio for a townhouse
For a townhouse buyer, FAR is the number that tells you whether the house can grow. If the listing sells you on “add a floor” or “extend the parlor,” the previous owner’s addition might have already used up the ratio.
Two things are worth checking. First, whether the house is already at or over its permitted FAR, which can occur with older buildings that predate current zoning and are legally nonconforming. Second, whether unused development rights could be sold to or bought from an adjacent lot, as in many NYC air-rights deals.
Both are questions for a land-use attorney, and the real estate glossary covers the terms. Run your purchase numbers, renovation included, on the closing cost calculators.
What do we check on a townhouse for a client?
When a client is serious about a townhouse, we look up the zoning before anyone falls in love with the garden. We pull the district and base FAR from ZoLa, estimate the built floor area against the lot, and flag whether the “potential” in the listing is real or decorative.
If expansion is part of why the client wants the house, that goes to an architect and a zoning attorney before the offer, not after. A commission rebate on a townhouse purchase is often large enough to cover the cost of early professional advice several times over.
Common questions
What does a FAR of 2.0 mean? It means the building’s total floor area can be up to twice the lot area. A 2,000-square-foot lot with a FAR of 2.0 permits up to 4,000 square feet of floor area.
How do I find the FAR limit for an NYC property? Look up the address on the Department of City Planning’s ZoLa map to get the zoning district, then check the district’s maximum residential FAR in the Zoning Resolution.
Does unused FAR add value? It can, if an addition is genuinely buildable. Height, yard, and setback rules, as well as landmark status, can render unused FAR unusable, so confirm with an architect before paying for it.
Can FAR be transferred between properties? In some cases, yes. Unused development rights can be transferred between adjacent lots within the same zoning district or, in special districts, further. These air-rights deals are complex and need a land-use attorney.
Nicole Fishman Benoliel co-founded NestApple in 2017. She's a lawyer admitted to the New York bar - her law degree is from La Escuela Libre de Derecho in Costa Rica, with further study at IE Business School in Madrid and an LLM from Fordham in New York. She does not act in a legal capacity at NestApple; every client is referred to an attorney who handles real estate deals full time.
