How To Calculate Far

Calculate the maximum allowable building floor area based on your lot size and local zoning regulations

Comprehensive Guide: How to Calculate Floor Area Ratio (FAR)

Floor Area Ratio (FAR), also known as Floor Space Ratio (FSR) or Floor Space Index (FSI), is a critical zoning regulation that determines how much building floor area can be constructed on a given lot. Understanding FAR is essential for developers, architects, urban planners, and property owners to maximize property potential while complying with local zoning laws.

What is Floor Area Ratio (FAR)?

FAR is the ratio of a building’s total floor area to the size of the lot upon which it is built. It’s expressed as a decimal number (e.g., 1.0, 2.5, 5.0) and represents how much building area can be constructed relative to the land area.

The basic FAR formula is:

FAR = (Total Building Floor Area) / (Lot Area)

Why FAR Matters in Urban Planning

FAR serves several important purposes in urban development:

• Density Control: Regulates how densely an area can be developed
• Infrastructure Planning: Helps cities plan for adequate roads, utilities, and services
• Neighborhood Character: Maintains the desired look and feel of different zones
• Property Value: Affects what can be built, impacting land values
• Sustainability: Influences walkability and transit efficiency

Step-by-Step Guide to Calculating FAR

1. Determine Your Lot Area

   Measure the total area of your property in square feet. This includes all land within your property boundaries. For irregular lots, you may need to use surveying techniques or GIS data.

2. Find Your Zoning District’s FAR

   Check your local zoning ordinance to find the maximum allowed FAR for your property. This information is typically available from:

   • City planning department websites
   • Zoning maps (often available as interactive GIS tools)
   • Property records from the county assessor
   • Professional zoning consultants

   Common FAR values by zone type:

   Zone Type	Typical FAR Range	Example Uses
   Single-Family Residential	0.2 – 1.0	Detached homes, duplexes
   Multi-Family Residential	1.0 – 3.0	Apartment buildings, townhomes
   Commercial	1.5 – 5.0	Offices, retail, hotels
   Industrial	0.5 – 2.0	Warehouses, light manufacturing
   Downtown/CBD	5.0 – 15.0+	Skyscrapers, mixed-use towers

3. Calculate Maximum Buildable Area

   Multiply your lot area by the FAR to determine the maximum allowable floor area:

   Maximum Floor Area = Lot Area × FAR

   For example, a 10,000 sq ft lot with FAR 2.0 allows 20,000 sq ft of total floor area.

4. Account for Setbacks and Other Restrictions

   Most zoning codes include additional requirements that affect buildable area:

   • Setbacks: Minimum distances buildings must be set back from property lines
   • Height Limits: Maximum building height restrictions
   • Open Space Requirements: Mandatory landscaped or unbuilt areas
   • Parking Requirements: Minimum parking spaces based on building use
   • Floor Area Bonuses: Additional FAR for including affordable housing or green features
5. Calculate Adjusted Buildable Area

   Subtract any non-buildable areas (setbacks, required open space) from your lot to determine the actual buildable footprint. Then calculate how many floors you can build within height limits.

6. Verify with Local Authorities

   Always confirm your calculations with the local planning department, as there may be:

   • Overlay zones with special requirements
   • Historical preservation restrictions
   • Environmental protection areas
   • Recent zoning code updates

Advanced FAR Considerations

While the basic FAR calculation is straightforward, several advanced factors can significantly impact your project:

Expert Insight:

According to the U.S. Department of Housing and Urban Development, “FAR regulations are among the most effective tools for shaping urban form and managing growth. Cities with well-designed FAR systems experience 15-20% more efficient land use than those with poorly implemented controls.”

Transfer of Development Rights (TDR)

Some cities allow developers to purchase additional FAR from other properties (often historic buildings or parks) to increase their buildable area. This market-based approach helps preserve important sites while enabling denser development where appropriate.

FAR Bonuses for Public Benefits

Many municipalities offer FAR bonuses for including:

• Affordable housing units (typically 10-20% of units)
• Green building certifications (LEED, Energy Star)
• Public plazas or open space
• Childcare facilities
• Art installations or cultural spaces

Floor Area Exclusions

Certain spaces are often excluded from FAR calculations:

• Basements (if below grade)
• Parking structures (in some jurisdictions)
• Mechanical equipment rooms
• Accessory dwelling units (ADUs) under certain sizes
• Green roofs or solar panel installations

FAR in Different U.S. Cities

FAR regulations vary significantly across the United States. Here’s a comparison of typical FAR values in major cities:

City	Downtown FAR	Residential FAR	Notable Policy
New York City	10-15+	1.0-3.5	Complex zoning with FAR bonuses for plazas and affordable housing
Chicago	12-20	1.2-3.0	Downtown density bonuses for transit-oriented development
San Francisco	8-12	0.8-2.5	Strict height limits despite high FAR in some districts
Los Angeles	6-13	0.5-3.0	Recent updates to allow more density near transit
Boston	8-15	1.0-2.5	Incentives for mixed-income housing
Washington D.C.	10-16	0.9-3.2	Height Act limits building heights to 130 ft in most areas

Common FAR Calculation Mistakes to Avoid

Even experienced developers sometimes make these errors:

1. Ignoring Gross vs. Net FAR: Some cities calculate FAR based on gross lot area (including streets), while others use net area (excluding public rights-of-way).
2. Forgetting About Floor Height: A high FAR doesn’t guarantee tall buildings if floor heights are restricted.
3. Overlooking Parking Requirements: Required parking can consume significant FAR, especially in car-dependent cities.
4. Misinterpreting Mixed-Use Ratios: Some zones require specific ratios between residential and commercial space.
5. Not Accounting for Phasing: Large projects may need to be built in phases, with each phase having its own FAR allocation.
6. Assuming Uniform FAR: FAR can vary dramatically even within the same zone based on specific parcel characteristics.

FAR and Property Value

The FAR designation significantly impacts land value. Properties with higher allowed FAR are generally more valuable because they can accommodate more development. According to research from the NYU Furman Center, in New York City:

• Each additional 1.0 FAR increases land value by approximately 25-35%
• Properties in zones with FAR 6.0+ can be worth 3-5 times more per square foot than those in FAR 1.0 zones
• The value premium is highest in areas with strong transit access and amenities

Developers often use the “residual land value” calculation to determine how much they can pay for a property based on its FAR potential:

Residual Land Value = (Project Revenue – Construction Costs – Financing Costs – Developer Profit) / Buildable Area (FAR × Lot Size)

FAR and Sustainable Development

Modern urban planning increasingly uses FAR as a tool for sustainability:

• Transit-Oriented Development: Higher FAR near transit hubs reduces car dependency
• Green Building Incentives: Many cities offer FAR bonuses for LEED-certified buildings
• Urban Heat Island Mitigation: Some zones reduce FAR requirements if buildings include green roofs
• Mixed-Use Development: Higher FAR for projects combining residential, commercial, and office uses
• Affordable Housing: FAR bonuses for including below-market-rate units

Academic Research:

A study from the Lincoln Institute of Land Policy found that cities with flexible FAR systems that reward sustainable practices see 30% higher development activity in transit-rich areas compared to cities with rigid FAR limits.

How to Increase Your Property’s FAR

If your property’s current FAR limits your development plans, consider these strategies:

1. Apply for a Zoning Variance

   Demonstrate that strict application of the FAR would cause unnecessary hardship. Success rates vary by jurisdiction but are highest for:

   • Irregularly shaped lots
   • Properties with unique topographical challenges
   • Historic buildings where preservation requires additional space
2. Utilize FAR Bonuses

   Take advantage of any available density bonuses for:

   • Affordable housing (most common bonus)
   • Green building certifications
   • Public art installations
   • Daycare facilities
   • Transit improvements
3. Purchase Transferable Development Rights

   In cities with TDR programs, you can buy additional FAR from:

   • Landmarked properties
   • Parks or open space
   • Properties in low-density zones
4. Combine Lots

   Assembling adjacent properties can:

   • Increase your total lot area
   • Potentially qualify for higher FAR in certain zones
   • Allow for more efficient building configurations
5. Negotiate with the City

   For significant projects, some cities will consider:

   • Planned Unit Developments (PUDs) with special FAR provisions
   • Public-private partnerships that include community benefits
   • Phased development agreements

The Future of FAR Regulations

FAR regulations are evolving to address modern urban challenges:

• Form-Based Codes: Some cities are replacing FAR with form-based codes that regulate building shape and street interaction rather than just floor area
• Dynamic FAR: Emerging systems adjust FAR based on real-time factors like transit capacity or environmental conditions
• Equity Considerations: New policies tie FAR bonuses to affordable housing and community benefits
• Climate Adaptation: Coastal cities are adjusting FAR to account for sea-level rise and flood risks
• Digital Tools: AI and GIS are enabling more precise FAR calculations and scenario modeling

FAR Calculator Tools and Resources

For more advanced calculations and local-specific information:

• Local Government Websites: Most city planning departments offer interactive zoning maps and FAR calculators
• Professional Software: Tools like AutoCAD, SketchUp, and ArcGIS include FAR calculation features
• Zoning Consultants: For complex projects, professional consultants can navigate FAR regulations and variance processes
• Online Calculators: Many real estate and development websites offer basic FAR calculators
• Academic Research: University urban planning departments often publish studies on FAR impacts

Case Study: FAR in Action

Let’s examine how FAR works in a real-world scenario for a mixed-use development in Chicago:

Property Details:

• Lot Size: 20,000 sq ft
• Zone: Downtown Mixed-Use (DX-7)
• Base FAR: 12.0
• Height Limit: 500 ft
• Setbacks: 10 ft on all sides

Development Plan:

• Ground floor: 15,000 sq ft retail
• Floors 2-10: 20,000 sq ft office per floor
• Floors 11-30: 15,000 sq ft residential per floor
• Total floor area: 435,000 sq ft

FAR Calculation:

435,000 sq ft / 20,000 sq ft lot = 21.75 FAR

How This Works:

• Base FAR: 12.0 (240,000 sq ft)
• Affordable Housing Bonus: +3.0 (20% affordable units = +60,000 sq ft)
• Green Building Bonus: +1.5 (LEED Gold = +30,000 sq ft)
• Transit Proximity Bonus: +2.0 (within 1/4 mile of transit = +40,000 sq ft)
• Public Plaza Bonus: +1.25 (1,000 sq ft public plaza = +25,000 sq ft)
• TDR Purchase: +2.0 (from nearby landmark = +40,000 sq ft)
• Total: 21.75 FAR (435,000 sq ft)

This example shows how developers can combine multiple strategies to achieve significantly higher density than the base FAR would allow.

Frequently Asked Questions About FAR

Q: Can FAR be changed?

A: Yes, but it requires a zoning change, which is a complex political process involving public hearings and city council approval. Success depends on demonstrating that the change benefits the community.

Q: Does FAR include parking?

A: It depends on the jurisdiction. Some cities include parking in FAR calculations, while others exclude it or count it at a reduced rate (e.g., 50%). Always check local regulations.

Q: How does FAR relate to building height?

A: FAR determines total floor area, while height limits restrict vertical growth. A high FAR with low height limits results in a sprawling building, while low FAR with high height limits allows for tall, slender towers.

Q: What’s the difference between FAR and lot coverage?

A: Lot coverage refers to the percentage of the lot that can be covered by buildings when viewed from above (typically 30-70%), while FAR measures total floor area across all stories.

Q: Can I transfer unused FAR to another property?

A: In cities with Transferable Development Rights (TDR) programs, yes. The process involves selling your unused development potential to another property owner.

Q: How does FAR affect property taxes?

A: Higher FAR potential generally increases property assessments and taxes, as the land is considered more valuable for development. However, the completed building will also generate more tax revenue.

Q: Are there different FAR rules for different building uses?

A: Yes, most zoning codes have different FAR limits for residential, commercial, industrial, and mixed-use developments. Some zones also have sublimits for specific uses (e.g., maximum 20% commercial in a mixed-use building).

Conclusion: Mastering FAR for Successful Development

Understanding and effectively utilizing Floor Area Ratio is essential for anyone involved in real estate development or urban planning. By mastering FAR calculations and strategies, you can:

• Maximize the potential of your property
• Navigate complex zoning regulations
• Create more valuable and sustainable developments
• Contribute to well-planned, livable communities
• Make informed investment decisions

Remember that FAR is just one tool in the zoning toolbox. Successful projects require considering FAR in conjunction with height limits, setbacks, use restrictions, and community needs. When in doubt, consult with local planning officials or professional zoning consultants to ensure your project complies with all regulations while achieving your development goals.

As cities continue to grow and evolve, FAR regulations will play an increasingly important role in shaping our built environment. Staying informed about FAR trends and best practices will give you a competitive edge in the real estate and development industries.