Floor Area Ratio (FAR), also known as Floor Space Index (FSI) or Floor Space Ratio, is a planning and zoning regulation that governs the relationship between the total floor area of a building or buildings on a lot and the total area of that lot. FAR is typically expressed as a ratio, representing the total allowable floor area of all buildings on a lot divided by the total area of the lot itself. It is used by local governments and planning authorities to control the density and intensity of development within a specific area.