Floor Area Ratio (Zoning)
The zoning intensity number a site's buildable size turns on.
Example
You enter
- Building gross floor area (SF) 30000
- Lot area (SF) 20000
- Zoning FAR limit (0 = skip the cap check) 2
You get
- Floor area ratio (FAR) 1.5
- Max buildable (ft²) 40000
- Remaining (ft²) 10000
Checked against published worked examples from: Metropolitan Council (MN) / Portland Permitting & Development.
Details, formula, and sources
ScopeFAR = gross building floor area / lot area, and where a limit is set the maximum buildable floor area = FAR_limit x lot area. A 30,000 SF building on a 20,000 SF lot is FAR 1.5; a 2.0 cap allows 40,000 SF, so 10,000 SF of capacity remains. FAR caps bulk without dictating footprint or height -- a FAR of 1.0 is one story over the whole lot or two over half. The catch is the definition of floor area (whether parking, basements, and mechanical count), which varies by municipality; enter the gross figure the local code defines. A screening aid; the zoning ordinance and planning authority govern.
Formula or tableFAR = building_floor_area / lot_area; max_buildable = FAR_limit x lot_area; remaining = max_buildable - existing_floor_area.
Source and editionFloor area ratio, the municipal zoning intensity measure, by name; the zoning ordinance and planning authority govern.
Free accessFAR is a standard zoning ratio; the floor area and lot area come from the survey and the local zoning code's definition of countable floor area.
What governsEstimate. AHJ and licensed professional govern.
API field namesbuilding_floor_area_sf, lot_area_sf, far_limit, far, max_buildable_sf, remaining_sf
- Countable floor area varies municipalities differ on whether parking, basements, and mechanical space count; enter the locally-defined gross figurelocal zoning code
- Max buildable maximum buildable floor area = FAR_limit x lot areazoning convention