Floor Area Ratio (FAR) Calculator

Introduction

The Floor Area Ratio (FAR) is a critical metric in urban planning and real estate development that measures the relationship between a building's total floor area and the size of the plot of land upon which it is built. This Floor Area Ratio Calculator provides a simple, accurate way to determine the FAR for any building project by dividing the total floor area by the plot area. Understanding FAR is essential for developers, architects, urban planners, and property owners as it directly impacts what can be built on a specific piece of land and helps ensure compliance with local zoning regulations and building codes.

FAR serves as a fundamental control mechanism in urban development, helping municipalities manage density, prevent overcrowding, and maintain the character of neighbourhoods. Whether you're planning a new construction project, evaluating an existing property, or simply trying to understand zoning requirements, our FAR calculator offers a straightforward solution for quick and accurate calculations.

Formula/Calculation

The Floor Area Ratio is calculated using a simple mathematical formula:

$FAR = \frac{Total\ Building\ Area}{Plot\ Area}$

Where:

• Total Building Area is the sum of the floor areas of all levels of the building (measured in square feet or square metres)
• Plot Area is the total area of the land parcel (measured in the same units as the building area)

For example, if a building has a total floor area of 20,000 square feet and sits on a plot of land that is 10,000 square feet, the FAR would be:

$FAR = \frac{20,000\ sq.ft.}{10,000\ sq.ft.} = 2.0$

This means the total floor area of the building is twice the size of the plot area.

Important Considerations

1. Consistent Units: Both the building area and plot area must be measured in the same units (either square feet or square metres).

2. Building Area Calculation: The total building area typically includes all enclosed spaces across all floors, but local regulations may specify certain exclusions or inclusions:

   • Some jurisdictions exclude mechanical spaces, parking areas, or basements
   • Others might include covered but unenclosed areas like balconies or porches at a reduced ratio

3. Rounding: FAR values are typically expressed to two decimal places for precision in zoning regulations.

Step-by-Step Guide

Using our Floor Area Ratio Calculator is straightforward:

1. Gather Your Measurements

   • Determine the total floor area of your building (sum of all floors)
   • Measure the total area of your plot of land
   • Ensure both measurements use the same units (square feet or square metres)

2. Enter Your Data

   • Input the total building area in the first field
   • Input the plot area in the second field

3. Review Your Results

   • The calculator will instantly display your FAR
   • The calculation formula will be shown for reference
   • A visual representation will help you understand the relationship between your building and plot

4. Interpret the Results

   • A higher FAR indicates a more densely developed property
   • Compare your result with local zoning requirements to ensure compliance
   • Use the result for planning purposes or zoning applications

5. Save or Share Your Calculation

   • Use the copy button to save the result for your records
   • Reference the calculation in permit applications or development proposals

Use Cases

Floor Area Ratio calculations are essential in numerous scenarios across urban planning, architecture, real estate, and property development:

1. Zoning Compliance

Most municipalities establish maximum FAR values for different zones to control development density. Developers and architects must calculate FAR during the design phase to ensure projects comply with these regulations. For example, a residential zone might have a maximum FAR of 0.5, while a downtown commercial district could allow an FAR of 10 or higher.

2. Property Valuation

Real estate appraisers and investors use FAR to assess property development potential. A property with unused FAR (where the current building doesn't utilize the maximum allowed ratio) may have significant development value. For instance, a property with a current FAR of 1.2 in a zone that allows an FAR of 3.0 has substantial untapped development potential.

3. Urban Planning

City planners use FAR as a tool to shape urban environments. By setting different FAR limits in various neighbourhoods, they can:

• Create high-density cores in downtown areas
• Preserve the character of historic districts
• Ensure appropriate transitions between commercial and residential zones
• Manage infrastructure load and traffic patterns

4. Development Feasibility Studies

Developers conduct feasibility studies using FAR calculations to determine the maximum buildable area on a site, which directly impacts project economics. For example, when evaluating a 20,000 square foot lot with an allowable FAR of 2.5, a developer knows they can build up to 50,000 square feet of floor area.

5. Building Renovations and Additions

Property owners planning renovations must calculate the existing FAR to determine if there's room for expansion under current zoning regulations. If a building already exceeds the currently allowed FAR (as might happen with older structures under newer zoning laws), additions may be restricted or require special variances.

6. Transfer of Development Rights (TDR)

In some jurisdictions, unused FAR can be transferred between properties through TDR programs. Calculating the precise FAR is essential to determine how many development rights can be sold or purchased.

Alternatives

While FAR is a widely used metric for regulating building density, several alternative or complementary measures exist:

1. Lot Coverage Ratio: Measures the percentage of the lot covered by building footprint, focusing on ground-level density rather than vertical development.

2. Building Height Restrictions: Directly limit the vertical dimension of buildings, often used in conjunction with FAR.

3. Setback Requirements: Specify minimum distances between buildings and property lines, indirectly affecting buildable area.

4. Unit Density: Regulates the number of dwelling units per acre, particularly relevant for residential developments.

5. Floor Area per Occupant: Used in building codes to ensure adequate space for health and safety, especially in residential and office buildings.

6. Open Space Ratio: Requires a minimum percentage of the lot to remain as open space, complementing FAR by ensuring undeveloped areas.

Each of these alternatives addresses different aspects of development control, and many jurisdictions use a combination of these metrics to achieve desired urban forms.

History

The concept of Floor Area Ratio emerged in the early 20th century as cities began implementing more sophisticated zoning regulations to manage urban growth. New York City's groundbreaking 1916 Zoning Resolution was among the first to incorporate FAR-like concepts, though the term itself wasn't widely used until later.

Key Milestones in FAR Development:

1. 1916: New York City's Zoning Resolution introduced building envelope controls that, while not explicitly using FAR, established the foundation for density regulation.

2. 1940s-1950s: The concept of FAR became more formalised in urban planning theory as modernist approaches to city planning gained prominence.

3. 1961: New York City's comprehensive zoning revision explicitly incorporated FAR as a primary regulatory tool, setting a precedent for other municipalities.

4. 1970s-1980s: FAR regulations became increasingly sophisticated, with cities implementing varying ratios for different districts and introducing bonus systems to incentivise desired development features like public plazas or affordable housing.

5. 1990s-Present: Many cities have refined their FAR regulations to promote smart growth, transit-oriented development, and sustainability goals. Some jurisdictions have implemented form-based codes that work alongside or replace traditional FAR controls.

The evolution of FAR regulations reflects changing urban planning philosophies and societal priorities. Early implementations focused primarily on preventing overcrowding and ensuring adequate light and air. Modern approaches often use FAR as part of a comprehensive strategy to create vibrant, mixed-use neighbourhoods, encourage sustainable development patterns, and preserve community character.

Today, FAR remains a fundamental tool in urban planning worldwide, though its application varies significantly across different cities and countries. In some regions, it may be known by different terms such as Floor Space Index (FSI) in India, Plot Ratio in the United Kingdom and Hong Kong, or Site Intensity in parts of Europe.

Code Examples

Here are examples of how to calculate Floor Area Ratio in various programming languages:

1' Excel formula for FAR calculation
2=B2/C2
3' Where B2 contains the total building area and C2 contains the plot area
4
5' Excel VBA Function
6Function CalculateFAR(BuildingArea As Double, PlotArea As Double) As Double
7    If PlotArea <= 0 Then
8        CalculateFAR = CVErr(xlErrValue)
9    Else
10        CalculateFAR = BuildingArea / PlotArea
11    End If
12End Function
13

1def calculate_far(building_area, plot_area):
2    """
3    Calculate Floor Area Ratio (FAR)
4    
5    Args:
6        building_area (float): Total floor area of the building in sq ft or sq m
7        plot_area (float): Total area of the plot in the same units
8        
9    Returns:
10        float: The calculated FAR or None if inputs are invalid
11    """
12    if building_area <= 0 or plot_area <= 0:
13        return None
14    
15    return building_area / plot_area
16
17# Example usage
18total_building_area = 25000  # sq ft
19plot_area = 10000  # sq ft
20far = calculate_far(total_building_area, plot_area)
21print(f"Floor Area Ratio: {far:.2f}")
22

1/**
2 * Calculate Floor Area Ratio (FAR)
3 * @param {number} buildingArea - Total floor area of the building
4 * @param {number} plotArea - Total area of the plot
5 * @returns {number|null} - The calculated FAR or null if inputs are invalid
6 */
7function calculateFAR(buildingArea, plotArea) {
8    if (buildingArea <= 0 || plotArea <= 0) {
9        return null;
10    }
11    
12    return buildingArea / plotArea;
13}
14
15// Example usage
16const totalBuildingArea = 15000; // sq ft
17const plotArea = 5000; // sq ft
18const far = calculateFAR(totalBuildingArea, plotArea);
19console.log(`Floor Area Ratio: ${far.toFixed(2)}`);
20

1public class FARCalculator {
2    /**
3     * Calculate Floor Area Ratio
4     * 
5     * @param buildingArea Total floor area of the building
6     * @param plotArea Total area of the plot
7     * @return The calculated FAR or -1 if inputs are invalid
8     */
9    public static double calculateFAR(double buildingArea, double plotArea) {
10        if (buildingArea <= 0 || plotArea <= 0) {
11            return -1; // Invalid input
12        }
13        
14        return buildingArea / plotArea;
15    }
16    
17    public static void main(String[] args) {
18        double totalBuildingArea = 30000; // sq ft
19        double plotArea = 10000; // sq ft
20        
21        double far = calculateFAR(totalBuildingArea, plotArea);
22        if (far >= 0) {
23            System.out.printf("Floor Area Ratio: %.2f%n", far);
24        } else {
25            System.out.println("Invalid input values");
26        }
27    }
28}
29

1public class FARCalculator
2{
3    /// <summary>
4    /// Calculate Floor Area Ratio (FAR)
5    /// </summary>
6    /// <param name="buildingArea">Total floor area of the building</param>
7    /// <param name="plotArea">Total area of the plot</param>
8    /// <returns>The calculated FAR or null if inputs are invalid</returns>
9    public static double? CalculateFAR(double buildingArea, double plotArea)
10    {
11        if (buildingArea <= 0 || plotArea <= 0)
12        {
13            return null;
14        }
15        
16        return buildingArea / plotArea;
17    }
18    
19    // Example usage
20    public static void Main()
21    {
22        double totalBuildingArea = 40000; // sq ft
23        double plotArea = 8000; // sq ft
24        
25        double? far = CalculateFAR(totalBuildingArea, plotArea);
26        if (far.HasValue)
27        {
28            Console.WriteLine($"Floor Area Ratio: {far.Value:F2}");
29        }
30        else
31        {
32            Console.WriteLine("Invalid input values");
33        }
34    }
35}
36

Practical Examples

Here are some practical examples of FAR calculations for different types of buildings:

Example 1: Single-Story Commercial Building

• Building footprint: 5,000 sq ft
• Number of floors: 1
• Total building area: 5,000 sq ft
• Plot area: 10,000 sq ft
• FAR = 5,000 ÷ 10,000 = 0.5

This low-density development uses only half of the potential building space relative to the plot size.

Example 2: Mid-Rise Apartment Building

• Building footprint: 10,000 sq ft
• Number of floors: 5
• Total building area: 50,000 sq ft
• Plot area: 20,000 sq ft
• FAR = 50,000 ÷ 20,000 = 2.5

This represents a medium-density development typical of urban residential areas.

Example 3: High-Rise Office Tower

• Building footprint: 15,000 sq ft
• Number of floors: 30
• Total building area: 450,000 sq ft
• Plot area: 30,000 sq ft
• FAR = 450,000 ÷ 30,000 = 15.0

This high FAR is characteristic of central business districts in major cities.

Example 4: Mixed-Use Development

• Retail space (ground floor): 20,000 sq ft
• Office space (floors 2-5): 80,000 sq ft
• Residential space (floors 6-10): 100,000 sq ft
• Total building area: 200,000 sq ft
• Plot area: 25,000 sq ft
• FAR = 200,000 ÷ 25,000 = 8.0

This represents a dense, mixed-use development that maximises land utilisation.

FAR Comparison by Building Type and Zone

Note: These ranges are illustrative and actual FAR limits vary significantly by jurisdiction.

FAQ

What is Floor Area Ratio (FAR)?

Floor Area Ratio (FAR) is a measurement that expresses the relationship between a building's total usable floor space and the size of the plot of land on which it is built. It is calculated by dividing the total floor area of all buildings on a lot by the area of the lot.

Why is FAR important in urban planning?

FAR is a crucial zoning tool that helps municipalities control development density, manage infrastructure capacity, prevent overcrowding, and maintain neighbourhood character. It directly influences the size and scale of buildings that can be constructed on a given plot of land.

How do I calculate Floor Area Ratio?

To calculate FAR, divide the total floor area of all levels of all buildings on a lot by the area of the lot. For example, if a 10,000 square foot lot contains a building with a total floor area of 25,000 square feet, the FAR is 2.5.

What is considered a high or low FAR?

FAR values typically range from less than 1.0 in suburban or low-density areas to 15.0 or higher in dense urban centres. A FAR below 1.0 means the total floor area is less than the lot size, while a FAR above 1.0 indicates the floor area exceeds the lot size (through multiple stories).

Does FAR include basements and mechanical spaces?

This varies by jurisdiction. Some municipalities exclude basements, mechanical rooms, parking areas, or other specific spaces from FAR calculations, while others include them. Always check local zoning codes for specific definitions of what floor areas count toward FAR.

How does FAR differ from lot coverage?

While FAR measures the ratio of total floor area (across all floors) to lot size, lot coverage measures only the percentage of the lot covered by the building footprint at ground level. A tall, slender building might have a high FAR but low lot coverage.

Can FAR requirements be exceeded?

In many jurisdictions, developers can exceed base FAR limits through various incentive programs or bonuses. Common mechanisms include providing public amenities, affordable housing, green building features, or purchasing development rights from other properties.

How does FAR affect property value?

Properties with higher allowable FAR typically have greater development potential and may command higher values. Investors and developers often seek properties where the existing buildings utilise less than the maximum allowed FAR, creating opportunity for expansion or redevelopment.

Is FAR the same worldwide?

While the basic concept is similar, FAR may be known by different names in various countries, such as Floor Space Index (FSI) in India, Plot Ratio in the UK and Hong Kong, or Site Intensity in parts of Europe. Calculation methods and regulatory approaches also vary by jurisdiction.

How do I find the maximum allowed FAR for my property?

Maximum allowed FAR is determined by local zoning regulations. Contact your municipal planning or zoning department, check the zoning code online, or consult with a local architect or land use attorney to determine the specific FAR limits for your property.

References

1. Barnett, J. (2011). City Design: Modernist, Traditional, Green and Systems Perspectives. Routledge.

2. Berke, P. R., Godschalk, D. R., Kaiser, E. J., & Rodriguez, D. A. (2006). Urban Land Use Planning. University of Illinois Press.

3. Joshi, K. K., & Kono, T. (2009). "Optimisation of floor area ratio regulation in a growing city." Regional Science and Urban Economics, 39(4), 502-511.

4. Talen, E. (2012). City Rules: How Regulations Affect Urban Form. Island Press.

5. American Planning Association. (2006). Planning and Urban Design Standards. Wiley.

6. NYC Department of City Planning. "Glossary of Planning Terms." https://www1.nyc.gov/site/planning/zoning/glossary.page

7. Lehnerer, A. (2009). Grand Urban Rules. 010 Publishers.

8. Pont, M. B., & Haupt, P. (2010). Spacematrix: Space, Density and Urban Form. NAi Publishers.

Conclusion

The Floor Area Ratio (FAR) is a fundamental concept in urban planning and real estate development that provides a standardised way to measure and regulate building density. By understanding how to calculate and interpret FAR, property owners, developers, architects, and planners can make informed decisions about land use and ensure compliance with local zoning regulations.

Our Floor Area Ratio Calculator simplifies this essential calculation, allowing you to quickly determine the FAR for any property or development project. Whether you're evaluating an existing building, planning a new development, or simply trying to understand the development potential of a property, this tool provides the accurate information you need.

Remember that while FAR is a universal concept, specific regulations and calculation methods may vary by jurisdiction. Always consult your local zoning code or planning department for the exact requirements that apply to your property.

Ready to calculate the Floor Area Ratio for your project? Enter your building and plot areas above to get started!