Floor Area Ratio (FAR)

What Is Floor Area Ratio (FAR)?

Floor area ratio, or FAR, is a zoning measure that compares a building's floor area with the size of the lot it occupies. Local governments use FAR to regulate building bulk, density, development potential, and how much usable floor area can be built on a parcel.

FAR matters financially because it can affect land value, redevelopment potential, housing supply, project feasibility, and what a buyer can legally build. The same lot can be worth very different amounts depending on its allowed FAR and zoning rules.

Formula

The basic FAR formula is:

For example, a 10,000-square-foot lot with 20,000 square feet of counted floor area has an FAR of 2.0. If zoning allows an FAR of 3.0, the same lot may allow up to 30,000 square feet of counted floor area, subject to height, setback, use, parking, open-space, and other rules.

How FAR Works in Zoning

FAR is one tool in a larger zoning system. It controls total bulk, but it does not by itself determine building shape. A building with the same FAR can be short and wide or taller and narrower if the zoning code allows that form.

Local rules define what counts toward floor area. Basements, mechanical space, parking, balconies, stairwells, affordable housing bonuses, and certain community facilities may be treated differently depending on jurisdiction. That is why the same simple formula can have complex real-world application.

Development Value

FAR turns zoning into economics. If a parcel is allowed more buildable floor area, a developer may be able to spread land cost across more apartments, offices, hotel rooms, or retail space. That can raise the price a buyer is willing to pay for the land.

The reverse is also true. A low FAR can limit revenue potential even on a desirable site. A property may have great location value but still be constrained if the zoning code does not allow enough floor area to support the desired project.

FAR and Air Rights

In some markets, unused development rights are informally called air rights. If a building uses less floor area than zoning allows, the unused capacity may have value if local law allows it to be transferred, merged, or used in a future expansion.

Those rights are technical. Lot mergers, transfer rules, landmark restrictions, environmental review, and neighbor agreements can affect whether unused FAR can actually become buildable space. The paper number is only the starting point.

Reading FAR in a Deal

In a real estate underwriting model, FAR should be tested against more than the headline zoning number. A parcel may have enough allowable floor area but still fail because of construction cost, required setbacks, historic restrictions, parking rules, inclusionary housing requirements, financing terms, or neighborhood opposition. Developers often compare maximum legal floor area with the floor area that is actually buildable and economically rentable. That gap can decide whether land is truly underused or only looks underused on paper. It also helps separate speculative land pricing from development capacity that can realistically be converted into income.

The Bottom Line

Floor area ratio is a compact way to measure allowable building density. It is simple mathematically, but financially powerful because it shapes what can be built, how land is valued, and whether a real estate project can work.