What it means
A multistorey building can contain much more total floor area than the ground it covers. FAR captures that relationship by adding the counted area across floors and comparing it with the site, which makes it different from a simple footprint or site-coverage percentage.
The denominator is the relevant lot area under the applicable rules, and the numerator is the area those rules count, which may exclude or treat certain spaces differently, so gross construction area, usable area and planning floor area are not automatically interchangeable. A ratio of 2 means the counted floor area is twice the lot area.
On a 1,000-square-metre lot, that would correspond to 2,000 square metres of counted floor area, and it does not mean the building must have exactly two storeys or occupy the entire site. Different designs can produce the same ratio, since a broad low-rise building and a smaller-footprint taller building may have similar total counted area, although height, setbacks, open space and other constraints can still make only one design permissible.
Planning authorities use FAR as one part of density control. The New York City zoning resolution, for example, specifies maximum ratios in particular districts and describes conditions for additional floor area, but those rules are location-specific and should not be generalised into a universal allowable ratio.
Before committing, obtain a planning interpretation for the actual site and proposed use. Development economics depend on usable and revenue-producing space as well as permitted area.
A project with substantial circulation or service space may produce less rental income than its headline floor area suggests, so the financial model should identify the area basis used for rent and construction cost. Reconcile the architect's area schedule with the financial model, because a mistake in area definitions can overstate both permitted construction and expected sale or rental proceeds.
A higher permitted ratio can create an opportunity to build more, but it does not guarantee greater profit. Extra floors can require expensive structure, lifts, safety systems or other infrastructure, and demand and financing capacity may limit the sensible size below the planning maximum.
Land valuation often reflects development potential, making FAR relevant to investment decisions. However, a site may also have restrictions, contamination, access issues or approval conditions, so a ratio extracted from a listing is only one input to due diligence.
In practice
Real-world examples.
Example
A site of 800 square metres supports a design with 1,600 square metres of counted floor area. Its FAR is 2. The same calculation does not prove that its proposed height, access or building use complies with local requirements.
Example
Two designs have the same total counted area. One has a wider footprint and fewer floors, while the other is taller. They can share the same FAR but face different setbacks, height limits and construction costs.
Example
A developer multiplies permitted floor area by a rent per square metre based on usable space. The result overstates income because corridors and service areas are not rented on the same basis. The model needs consistent area definitions.
Formula
Calculation
FAR = counted floor area / relevant lot area.
Worked example. With 3,000 square metres of counted area on a 1,200-square-metre lot, FAR = 3,000 / 1,200 = 2.5. If a hypothetical permitted FAR is 3, the arithmetic area ceiling is 3 x 1,200 = 3,600 square metres, before other restrictions and exclusions.
Revenue check. Suppose only 2,400 of the 3,000 square metres of counted area is lettable, which is 2,400 / 3,000 x 100 = 80% efficiency. At an assumed rent of $300 per lettable square metre per year, annual rent is 2,400 x $300 = $720,000, not the $900,000 that the full 3,000 square metres would suggest.
This is not a zoning determination for any actual site.Case study
Seen in the real world.
Fictional case: Stonefield Development values land using a high advertised FAR. Its architect finds that the proposed use and setbacks reduce the feasible design, while some constructed space earns no rent. The team revises both the area schedule and project cash flows before making an offer. It avoids paying for theoretical capacity that the actual project cannot economically use.
Stonefield also asks the planning consultant for a written interpretation of the counted area on its preferred scheme. The consultant's answer excludes some plant space, which lowers the ceiling slightly but makes the area schedule match the planning basis. The land offer is then set against the revised, narrower figure.
Watch out
Common mistakes.
- Confusing total floor area ratio with building-footprint coverage or story count.
- Using gross, usable and planning area as though they were the same measure.
- Treating a permitted ratio as proof that the full project is approved or profitable.
Questions
People also ask.
Does FAR equal the number of floors?
No. Floor count and footprint interact. Different shapes can have the same total counted area and ratio.
Do all authorities count the same spaces?
No. Local definitions, exclusions and bonuses vary. Use the applicable rules and area schedule.
Is higher FAR always better financially?
No. Extra capacity can involve higher construction costs or insufficient demand. The economic project may be smaller than the theoretical planning maximum.
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