Understanding the Floor Area Ratio (FAR) is essential for real estate developers, urban planners, and homeowners looking to expand their property. FAR is a key metric used by local governments to regulate the density of buildings in specific zones.
FAR Calculator
What is Floor Area Ratio (FAR)?
Floor Area Ratio (FAR) is the relationship between the total amount of usable floor area that a building has, or has been permitted for, and the total area of the lot on which the building stands. It is a decimal figure that represents the density of a building project.
A higher FAR indicates a greater building density. For example, in high-density urban centers like Manhattan or Tokyo, FAR values can be very high, whereas in suburban residential areas, the FAR is typically much lower to ensure open space and less congestion.
The FAR Formula
The mathematical formula for calculating FAR is quite simple:
Step-by-Step Calculation Guide
To calculate the FAR of a property, follow these four steps:
- Step 1: Determine the Gross Floor Area (GFA). This is the sum of the floor area of all levels of the building. Note: Local zoning laws may exclude certain areas like basements, parking garages, or mechanical rooms.
- Step 2: Determine the Total Lot Area. This is the total square footage (or square meters) of the land parcel the building sits on.
- Step 3: Divide GFA by Lot Area. Take the number from Step 1 and divide it by the number from Step 2.
- Step 4: Interpret the Result. A result of 1.0 means you can build a structure with a total floor area equal to the lot size. A result of 0.5 means the building can only be half the size of the lot.
Real-World Examples
Example 1: Single Story Building
If you have a 5,000 square foot lot and you build a 2,500 square foot single-story house, your FAR is 0.5 (2,500 / 5,000).
Example 2: Multi-Story Building
If you have that same 5,000 square foot lot but build a 2-story building where each floor is 2,500 square feet, your total floor area is 5,000 square feet. Your FAR is 1.0 (5,000 / 5,000).
Example 3: High Density
If you build a 4-story building on that 5,000 square foot lot, and each floor is 2,500 square feet, the total floor area is 10,000 square feet. Your FAR is 2.0 (10,000 / 5,000).
Why is FAR Important?
FAR is a critical tool for urban planning for several reasons:
- Zoning Compliance: Cities set maximum FAR limits to control the "bulk" of buildings and ensure the local infrastructure (roads, water, electricity) can handle the population density.
- Property Value: Generally, a higher allowable FAR increases the value of a piece of land because it allows for more square footage to be developed (and thus more units to be sold or rented).
- Environmental Impact: FAR helps maintain a balance between built-up areas and open green spaces, which is vital for managing heat islands and stormwater runoff.
Common Exclusions in FAR
It is important to check your local zoning ordinances, as many cities allow you to exclude specific areas from the GFA calculation. Common exclusions include:
- Unfinished basements or attics.
- Open-air balconies or porches.
- Parking structures or garages.
- Elevator shafts and stairwells.