Floor area ratio (FAR) is the ratio of a building's total floor area (gross floor area) to the size of the piece of land upon which it is built. It is often used as one of the regulations in city planning along with the building-to-land ratio. The terms can also refer to limits imposed on such a ratio through zoning. FAR includes all floor areas but is indifferent to their spatial distribution on the lot whereas the building coverage ratio (or lot coverage) measures building footprint on the lot but is indifferent to building height.

Written as a formula, FAR = gross floor area/area of the plot.

Lower maximum-allowed floor area ratios are linked to lower land values and lower housing density.