Floor Area Ratio (FAR) Calculator
Instantly determine the Floor Area Ratio (FAR) of your property. Enter the building and lot area to understand your development potential and how to calculate Floor Area Ratio far for zoning and planning.
Visual comparison of Lot Area vs. Total Building Floor Area.
What is Floor Area Ratio (FAR)?
Floor Area Ratio (FAR) is a critical zoning and real estate development metric that defines the relationship between a building’s total floor area and the area of the lot it is built on. Expressed as a ratio (e.g., 2.0, 5.5, or 0.5), it is a tool used by city planners and local governments to regulate the density of development in specific areas. A higher FAR allows for a larger, more dense building on a given piece of land, while a lower FAR restricts the size and encourages less density. Understanding how to calculate Floor Area Ratio far is fundamental for architects, developers, and real estate investors.
Essentially, FAR dictates the maximum allowable floor space you can build. For example, a 10,000 square foot lot with a FAR of 2.0 would allow for a building with a total floor area of 20,000 square feet. This could be a two-story building covering the entire lot or a four-story building covering half of the lot. The flexibility it provides within a set volume is a key feature.
Floor Area Ratio (FAR) Formula and Explanation
The calculation for FAR is straightforward. You divide the total gross floor area of the building by the total area of the plot of land.
FAR = Total Building Floor Area / Total Lot Area
It’s crucial that both the building area and the lot area are measured in the same units (e.g., square feet or square meters) for the ratio to be accurate. The resulting FAR is a unitless number.
Variables Table
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Total Building Floor Area | The sum of the floor areas of all stories of a building, measured to the exterior of the walls. Exclusions like basements or parking garages can vary by municipality. | Square Feet (sq ft) or Square Meters (sq m) | 1,000 – 1,000,000+ |
| Total Lot Area | The total horizontal area of the parcel of land on which the building is situated. | Square Feet (sq ft) or Square Meters (sq m) | 500 – 500,000+ |
| Floor Area Ratio (FAR) | The resulting ratio indicating development density. It is not a percentage. | Unitless | 0.2 (low density) – 15.0+ (high density urban core) |
Practical Examples
Example 1: Urban Commercial Development
A developer is looking at a 20,000 sq ft lot in a downtown area with a designated FAR of 8.0.
- Inputs:
- Total Lot Area: 20,000 sq ft
- Permitted FAR: 8.0
- Calculation: Maximum Buildable Area = 20,000 sq ft * 8.0 = 160,000 sq ft
- Result: The developer can construct a building with a total gross floor area of up to 160,000 square feet. This could be an 8-story building with a 20,000 sq ft footprint or a 16-story building with a 10,000 sq ft footprint.
Example 2: Suburban Residential Property
A homeowner has a 500 sq m lot in a suburban zone where the maximum FAR is 0.75 to maintain a low-density character.
- Inputs:
- Total Lot Area: 500 sq m
- Permitted FAR: 0.75
- Calculation: Maximum Buildable Area = 500 sq m * 0.75 = 375 sq m
- Result: The homeowner can build a house with a total floor area of no more than 375 square meters. To find the FAR of an existing house, if the house has a total area of 300 sq m on that lot, the calculation is 300 / 500, resulting in a FAR of 0.6. This is a common question when checking zoning regulations calculator information.
How to Use This Floor Area Ratio Calculator
Our tool makes learning how to calculate Floor Area Ratio far simple and intuitive.
- Select Units: Start by choosing your preferred unit of measurement, either Square Feet (sq ft) or Square Meters (sq m), from the dropdown menu. Ensure you use the same unit for both inputs.
- Enter Total Building Floor Area: Input the total gross floor area of your building. This should include the area of all floors.
- Enter Total Lot Area: Input the total area of the land parcel.
- Review the Results: The calculator will instantly display the Floor Area Ratio (FAR) in the results section. You will see the primary FAR value, a breakdown of your inputs, and a visual chart comparing the two areas.
- Interpret the Chart: The bar chart provides a quick visual understanding of how the building’s size compares to the lot’s size, helping you conceptualize the density.
Key Factors That Affect Floor Area Ratio
FAR is not a universal constant; it is highly dependent on local regulations and planning goals. For those exploring the maximum buildable area, several factors are key.
- Zoning Regulations: This is the most significant factor. Each city is divided into zones (e.g., residential, commercial, industrial), and each zone has its own set of rules, including a maximum FAR.
- Location and Population Density: Dense urban cores like Manhattan or downtown Chicago will have much higher allowable FARs (sometimes exceeding 15.0) than suburban or rural areas (often below 1.0).
- Type of Use: The intended use of the property (e.g., commercial property FAR vs. residential) often influences the permitted FAR. Commercial zones typically allow for higher density.
- Infrastructure Capacity: Local authorities set FAR limits based on the capacity of the surrounding infrastructure, such as roads, public transit, water, and sewage systems.
- Community Character: In historic districts or areas with a specific aesthetic, FAR is used to maintain the existing scale and character, preventing oversized developments.
- Incentives (Bonuses): Some cities offer “bonus” FAR in exchange for public amenities provided by the developer, such as a public plaza, affordable housing units, or transit improvements.
Frequently Asked Questions (FAQ)
FAR stands for Floor Area Ratio. It’s a key metric in urban planning and zoning.
Neither is inherently “better”; they serve different purposes. A higher FAR is desirable for developers in dense urban areas seeking to maximize a property’s potential. A lower FAR is better for communities aiming to preserve open space, reduce traffic, and maintain a low-density character.
This depends entirely on the local municipality’s zoning code. Often, areas that are not considered “habitable,” like basements used for storage, elevator shafts, or open-air balconies, are excluded from the FAR calculation. However, finished basements might be included. Always check local regulations.
Lot coverage is the percentage of the lot area that is covered by the building’s “footprint.” FAR, on the other hand, accounts for the total area of all floors. A tall, slender building could have low lot coverage but a very high FAR. Check out this guide on urban density explained for more details.
You need to consult the zoning ordinance or map for your specific address, which is usually available on your city or county’s planning department website. This information is a core part of any zoning 101 guide.
Yes. A FAR of less than 1.0 means the total floor area of the building is smaller than the total area of the lot. For example, a FAR of 0.4 on a 10,000 sq ft lot allows for a building of only 4,000 sq ft, which is common in single-family residential zones.
You must use the same unit for both the floor area and the lot area. If one is in square feet and the other in acres, for example, you must convert one before performing the calculation. Our calculator handles this automatically when you select a unit. (1 acre = 43,560 square feet).
A FAR of 2.0 means the total permitted floor area for a building is twice the area of the lot. For example, on a 1,000 sq ft lot, you can build a structure with 2,000 sq ft of total floor area.