What Is Floor Area Ratio (FAR)? How to Calculate It and What It Limits

Floor area ratio (FAR) is the total floor area of the buildings on a lot divided by the area of the lot. A zoning code sets a maximum FAR for each district, and multiplying that number by the lot area gives the most floor area that can be built. A FAR of 2.0 on a 20,000 square foot lot allows 40,000 square feet of floor area, in whatever shape the height, setback, and coverage rules permit.

How it works

FAR controls bulk, not shape, and codes write it as a decimal (2.0) or a ratio (2:1). On a 10,000 square foot lot with a FAR of 1.0, the 10,000 square feet of floor area could be one story covering the whole lot, two stories covering half of it, or four stories covering a quarter. Height limits, setbacks, and lot coverage decide which of those is possible.

Three details change the answer:

• What counts as floor area. Each code defines it. Parking, below-grade space, and mechanical rooms are common exclusions, but not universal ones.
• What counts as lot area. Some codes measure the gross lot, others subtract land dedicated for streets.
• Bonuses. Many cities let a project exceed the base FAR in exchange for affordable housing, fees, or public improvements, sometimes through an overlay district.

Not every code uses FAR. Many districts control size with height, lot coverage, and units per acre instead.

What it means if you are buying or developing land

• Value: maximum FAR times lot area is the starting point for land value per buildable square foot.
• The binding limit: FAR is a ceiling, and other rules often stop a project first. Height, setbacks, parking, and density caps can make the full FAR unreachable, so test all of them before pricing land on FAR alone.
• Cost of going higher: bonus floor area usually comes with fees or requirements that belong in the pro forma.
• Time and risk: building beyond the maximum without a bonus program means a variance or a rezoning, both discretionary and both measured in months.

FAR matters most for dense projects, such as those in our multifamily site selection guide and in mixed-use districts.

How real jurisdictions handle it

• New York City: the Department of City Planning's zoning glossary calls FAR the principal bulk regulation controlling the size of buildings. Its example: on a 10,000 square foot zoning lot in a district with a maximum FAR of 1.0, floor area cannot exceed 10,000 square feet. The Zoning Resolution's definition of floor area shows how much the details matter: it includes basement space but not cellar space, unless the cellar is used for dwelling purposes.
• Austin: a 2024 city review sheet for a 35,464 square foot downtown site zoned DMU (downtown mixed use) lists an allowed FAR of 5:1 and a proposed FAR of 20:1 under the Downtown Density Bonus Program. That is the difference between about 177,000 and 709,000 square feet of floor area. Bonus area up to 15:1 could be granted administratively, and the rest required City Council, which approved the increase to a maximum of 20:1 on December 12, 2024. The staff sheet lists $1,773,200 in affordable housing fees in lieu, on top of design, streetscape, and green building requirements. See our Austin zoning guide.

How to check a specific parcel

Find the district's maximum FAR in its development standards, then read the code's definition of floor area and lot area. Check for overlays and bonus programs, then test the result against height, setbacks, coverage, and parking. In Plotzy, filter parcels by zoning designation and lot size to find sites with enough capacity, and ask Zoning AI "What is the maximum FAR for this parcel, and what is excluded from floor area?" for an answer with the code section cited.

Frequently asked questions

How do you calculate floor area ratio?

Divide the total floor area of all buildings on the lot by the lot area. A 30,000 square foot building on a 15,000 square foot lot has a FAR of 2.0. To find what a site can hold, multiply the lot area by the district's maximum FAR.

Does FAR limit building height?

Not directly. FAR caps total floor area, and a separate height limit caps height.

Does parking count toward FAR?

It depends on the code's definition of floor area. Many codes exclude some or all structured parking, and some count it above grade.

What is the difference between FAR and lot coverage?

Lot coverage is the share of the lot covered by building footprint. FAR counts the floor area on every story. A four-story building covering half the lot has 50 percent coverage and a FAR of 2.0.

Sources

The statutes, codes, and agency documents cited on this page were checked on October 4, 2026. Laws and local codes are amended often, so confirm the current text before relying on any detail. This page is general information, not legal advice.

• NYC Department of City Planning: Glossary of Zoning Terms. The description of FAR and the 10,000 square foot example. The document is dated 2021 and is the glossary the department currently publishes.
• NYC Department of City Planning: Zoning Resolution Section 12-10. The definitions of floor area ratio and floor area, including basement and cellar space.
• City of Austin: Downtown Density Bonus Request Site Plan Review Sheet, Case SP-2024-0006C. Site area, zoning, allowed and proposed FAR, program requirements, and fees in lieu. This is the staff report, so its figures are the proposal as reviewed.
• City of Austin: Ordinance No. 20241212-079. The City Council's grant of additional FAR, from 15:1 to a maximum of 20:1.
• City of Austin: Regular Council Minutes, December 12, 2024. The vote on that ordinance (Item 79).