Floor Area Ratio (FAR): Meaning, Formula & Worked Example

Direct answer

What floor area ratio means, how to calculate the maximum buildable floor area on a lot, and a worked example architects can reuse. A key reference is illustrative residential far: 0.4–1.0; check the cited source, edition, units, and applicability before using it for design, compliance, procurement, or approval. FAR definition is Gross floor area ÷ lot area; a ratio, dimensionless. Illustrative residential FAR is 0.4–1.0; low-density districts. Illustrative downtown FAR is 3.0–12.0+; high-density / with bonuses. Floor area ratio (FAR) is the ratio of a building's total countable floor area to the area of its lot. It is dimensionless: Read the values with the cited source, edition or observation period, units and applicability; replace illustrative inputs with current project evidence before design, procurement or approval use.

Content and cited inputs reviewed by Harth team · Published 2026-08-14 · Updated 2026-08-14.

What does this term mean?

Floor Area Ratio (FAR): What floor area ratio means, how to calculate the maximum buildable floor area on a lot, and a worked example architects can reuse.

What does FAR stand for in real estate and construction?

FAR stands for floor area ratio. It is the amount of floor space a zoning code allows on a lot, stated as a multiple of the lot's own area, and it is the single number planners, developers and architects use first to size what a site can hold. A lot zoned at a FAR of 2.0 can carry countable floor area equal to twice its land area. Some jurisdictions use a different name for the same ratio: floor space ratio (FSR) in New South Wales planning instruments, and floor space index (FSI) in parts of India.

"Gross floor area" here means floor area as the local ordinance defines it — the counted total, after any exclusions the code allows.

Which parcel controls must be checked?

Floor area ratio (FAR) is the ratio of a building's total countable floor area to the area of its lot. It is dimensionless:

$$ \text{FAR} = \frac{\text{gross floor area}}{\text{lot area}} $$

A FAR of 1.0 means you can build floor area equal to the lot area — a single story covering the whole lot, or two stories covering half of it. FAR caps total floor area; height, setbacks, and lot coverage shape how that area is distributed.

Worked example

Assume a 10,000 sf lot in a district with a 2.0 FAR limit.

The same 20,000 sf can take many forms — a squat, wide building or a taller, slimmer one — as long as height and setback limits are met.

What a given FAR looks like on a 10,000 sf lot

FAR fixes total floor area, not shape. Dividing FAR by the share of the lot the building covers gives the number of storeys, assuming every floor has the same footprint and all of it counts:

Most districts also cap lot coverage, height and setbacks, so several cells in this table will be unbuildable on a real parcel; the table shows the arithmetic, not an entitlement.

Illustrative FAR ranges

These ranges are directional. The controlling FAR for a parcel — and what floor area actually counts toward it — comes from the local ordinance.

Is there a standard FAR?

No. There is no national or default FAR: each zoning district in each ordinance sets its own limit, and the figure moves when the ordinance is amended. Two official examples show how differently codes express it.

New York City sets residential FAR by district in Zoning Resolution sections 23-21 (R1–R5) and 23-22 (R6–R12), both last amended 5 December 2024 under City of Yes for Housing Opportunity:

ZR 23-21 also limits floor area tied to any single dwelling unit on standard R1–R5 lots of 4,000 sf or more to an equivalent FAR of 0.60, and some R6–R8 values differ within 100 feet of a wide street. These figures replaced earlier ones in December 2024, so older references may quote different numbers.

Chicago builds FAR into many district names. The city's Department of Buildings Zoning 101 guide (December 2019) gives DX-5 (maximum FAR 5.0) and B3-3 (maximum FAR 3.0) as examples, but notes RM-4.5 allows 1.70 — so the suffix is not a FAR in every district. Chicago also applies FAR to net site area (site area minus any public way), not the gross parcel.

For a real parcel, read the current ordinance text and official zoning map, then check overlays, special districts and bonus programs that change the base figure.

Where FAR meets the rest of the code

FAR rarely acts alone. A parcel might have generous FAR but be limited by height or setbacks before it can reach the FAR ceiling. Read FAR alongside the other bulk standards described in understanding zoning districts.

Test it on your site

Drop your lot dimensions into a Harth massing study, set the FAR and height limits for your district, and watch the buildable envelope resolve in real time — so you can see whether FAR or height is the binding constraint before schematic design.

Floor Area Ratio (FAR): Meaning, Formula & Worked Example: parcel-control verification record

Project-use verification: leave controls blank until the parcel, map, ordinance and overlays agree. The authority having jurisdiction and recorded approvals control.

Where can you explore related guidance?

• Explore all zoning guidance
• Zoning Districts Explained: Residential to Mixed-Use
• Residential Setback Requirements: Front, Side & Rear Explained
• Zoning in Austin, TX: District Families & Illustrative Standards

Sources and method

Concept explainer based on standard U.S. zoning practice. FAR limits, exemptions, and the exact definition of countable floor area vary by municipality; the local zoning ordinance is authoritative. FAR values shown are illustrative, not code citations. Official references: NYC Zoning Resolution. District FAR examples: NYC Zoning Resolution 23-21 and 23-22 (last amended 2024-12-05); Chicago Department of Buildings, Zoning 101 (2019-12-01); floor space ratio definition: NSW Standard Instrument LEP cl 4.5.

Source links

• zr.planning.nyc.gov

• zr.planning.nyc.gov

• zr.planning.nyc.gov

• chicago.gov

• classic.austlii.edu.au