Floor Area Ratio, the ratio of the total building floor area to the lot area, is a common measurement system used to regulated the density of buildings. Most cities use floor area ratio (FAR) as part of their zoning regulations. Both New York City and London use FAR, but they measure it in different ways, resulting in different representations in density.
NYC: FAR = Gross Floor Area / Lot Area
LD: FAR = Gross Floor Area / Street Center Line Area
In New York City, FAR is calculated relative to the lot area, were as in London FAR is calculated relative to the center line of the streets bounding the lot. The London method gives a better representation of the built density of a neighborhood as it takes into accounts streets and public spaces, but is difficult to use as regulatory mechanism. Below are several New York City neighborhoods measured using both FAR methodologies to illustrate the different representations of density.
Flatiron District
LD FAR: 5.3
NYC FAR: 8.0
Financial District
LD FAR: 11.3
NYC FAR: 18.0
Upper East Side
LD FAR: 4.4
NYC FAR: 7.1
Battery Park City North
LD FAR: 5.2
NYC FAR: 15.7
Tribeca
LD FAR: 3.8
NYC FAR: 7.0
Greenwich Village
LD FAR: 3.5
NYC FAR: 5.3