Land records · Parcel maps · October 5, 2026
What Is Floor Area Ratio (FAR) in Zoning?
Floor area ratio (FAR) compares a building's total floor area to its lot size. How FAR is calculated, examples, what counts, and how it shapes buildings.
What is floor area ratio? Floor area ratio (FAR) is a zoning measure that compares a building’s total floor area to the area of its lot. A FAR of 0.5 on a 10,000 square foot lot allows 5,000 square feet of floor area, whether as a one-story building covering half the lot or a two-story building covering a quarter. Cities use FAR to control building bulk and density. This page is general land-records background, not legal advice.
How to calculate FAR
FAR = total floor area ÷ lot area
| Lot area | Total floor area | FAR |
|---|---|---|
| 10,000 sq ft | 3,000 sq ft | 0.30 |
| 10,000 sq ft | 5,000 sq ft | 0.50 |
| 5,000 sq ft | 10,000 sq ft | 2.0 |
| 20,000 sq ft | 200,000 sq ft | 10.0 |
To find the maximum floor area, multiply lot area by the allowed FAR.
What counts as floor area
Definitions vary. Codes may count or exclude:
- Basements, depending on how far below grade they are.
- Attics with a minimum headroom.
- Garages and parking structures.
- Covered porches and balconies.
- Mechanical spaces.
Read the code’s definition of “floor area” or “gross floor area.”
FAR vs lot coverage
| Measure | Controls |
|---|---|
| Lot coverage | Footprint on the ground. See what is lot coverage |
| FAR | Total floor space across all stories |
| Height limit | Vertical size |
The three work together. A low coverage limit with a high FAR encourages taller buildings.
Where FAR is used
FAR is common in downtowns and commercial districts, and some cities apply it to single-family zones to limit very large houses on small lots. Many suburban codes rely on setbacks and height instead.
FAR bonuses and transfers
Some cities grant extra FAR for affordable housing, public plazas, or green building. Unused FAR can sometimes be sold to nearby properties through development rights programs. See what are air rights.
Lot area matters
FAR depends on accurate lot area, which comes from the plat, survey, or assessor. Right-of-way dedications can reduce the lot area used in calculations. See how to find acreage of property.
Finding the FAR limit
Check the zoning district’s dimensional table. See how to find zoning of a property.
FAR in practice for homeowners
Where FAR applies to houses, it can limit how big an addition or second story can be. Before designing, calculate existing floor area using the code’s definition, subtract it from the maximum, and see what remains. Designers sometimes use exempt spaces, such as certain basements or open porches, to stay within limits while adding usable room.
A worked example
Suppose a 6,000 square foot lot has a FAR limit of 0.45. The maximum floor area is 6,000 × 0.45 = 2,700 square feet. If the existing house has 1,800 square feet of countable floor area, an addition could add up to about 900 square feet, subject to setbacks, height, and coverage limits.
Bottom line
Floor area ratio compares total floor area to lot area and limits building size. Multiply lot area by the allowed FAR for maximum floor area, check what counts as floor area in your code, and consider coverage and height limits too. Look up lots on the Platbookmapper map.
What is floor area ratio FAQ
What does a FAR of 1.0 mean?
Total floor area can equal the lot area.
How do I calculate floor area ratio?
Divide total building floor area by lot area.
Do basements count toward FAR?
It depends on the code and how far below grade they are.
Is FAR the same as lot coverage?
No. FAR covers total floor area across stories; coverage covers footprint.
Can FAR be increased?
Some cities offer bonuses or allow transfers of unused FAR.