Calculate building density and zoning compliance
Floor Area Ratio (FAR) is the ratio of a building's total floor area to the size of the piece of land upon which it is built.
Local governments use FAR to limit the density of development in specific zones. A FAR of 1.0 means you can build a 1-story building covering the whole lot, or a 2-story building covering half.
Some zoning codes exclude basements, parking garages, or mechanical rooms from the FAR calculation. Check local ordinances.
Scenario: You own a 10,000 sq ft lot and want to build a 3-story office building with each floor being 5,000 sq ft. Is this allowed if the zoning code specifies FAR = 1.5?
Step 1: Calculate FAR = Total Floor Area ÷ Lot Area = 15,000 ÷ 10,000 = 1.5
Step 2: Compare to zoning limit: 1.5 = 1.5 ✓ Compliant
Result: Your proposed building exactly meets the FAR limit of 1.5. This is the maximum allowed development on this lot. Any additional floor area would violate the zoning code and require a variance.
FAR is the ratio of total building floor area to lot size. It measures development density. FAR = 1.0 means the building's total floor area equals the lot size (e.g., 10,000 sq ft building on 10,000 sq ft lot). FAR = 2.0 means twice the lot size.
FAR controls building density, which affects infrastructure (roads, utilities, parking), neighborhood character, and property values. Low-density residential areas might have FAR 0.5, while dense urban cores allow FAR 10-25 for high-rises.
Lot coverage is the percentage of the lot covered by the building's footprint (ground floor only). FAR includes all floors. You can have low lot coverage (30%) but high FAR (3.0) with a tall, narrow tower on a small footprint.
It depends on local code. Many jurisdictions exclude below-grade basements, parking garages, mechanical rooms, and open balconies from FAR calculations. Always check your local zoning ordinance—rules vary significantly by municipality.
FAR 0.5 means the total building floor area is half the lot size. On a 20,000 sq ft lot, you could build 10,000 sq ft total (e.g., a 10,000 sq ft single-story home, or a 5,000 sq ft two-story home). This is typical for low-density suburbs.
Low-density residential: FAR 0.3-0.8. Medium-density residential: FAR 1.0-2.5. High-density residential (apartments): FAR 2.5-8.0. Commercial/mixed-use: FAR 3.0-15.0. Dense urban centers (Manhattan, Hong Kong): FAR 10-25+.
Yes, but it's difficult. Variances require proving 'hardship'—that strict zoning enforcement prevents reasonable use of your property due to unique circumstances (odd lot shape, topography). Simply wanting more square footage isn't sufficient grounds for a variance.
Check your local zoning map and ordinance. The city/county planning department website usually has an online zoning map. Enter your address to find the zone designation (e.g., 'R-2', 'C-1') then look up that zone's FAR limit in the zoning code.
Disclaimer: Floor Area Ratio (FAR) calculations are theoretical estimates for planning purposes only. Local zoning codes vary significantly and may exclude certain areas (basements, parking, mechanical rooms) from FAR calculations. Some jurisdictions define FAR differently.
Important Note on Site Coverage: The "Building Density" output shown here is FAR as a percentage. True site coverage (lot coverage) requires the building's ground-floor footprint, not total floor area. This calculator shows FAR only. For accurate site coverage, consult your zoning department or surveyor.
Always consult your local zoning code, planning department, and city/county ordinances for accurate FAR limits and definitions applicable to your property. Consult a real estate attorney or professional for legal zoning compliance.
Related Tools