Floor Area Ratio (FAR) Calculator

About the Floor Area Ratio (FAR) Calculator

Calculates the floor area ratio (FAR) from total building floor area and lot area, or the maximum buildable floor area for a given FAR limit.

How to use this calculator

1. Enter the lot area in square feet or square meters, using the units required by your project.
2. Enter the total floor area, which is the sum of all enclosed floors in the building.
3. Read the FAR value to see how intensely the lot is being used.
4. Use the result to check whether a design fits zoning limits or to estimate the maximum floor area allowed.

The formula explained

The formula \( FAR = \frac{total\\ floor\\ area}{lot\\ area} \) computes how many times the lot area is covered by the building's floor area. A FAR of \(1.0\) means the total floor area equals the lot area, while \(2.0\) means the total floor area is twice the lot area.

• \(\text{FAR}\) = floor area ratio
• \(\text{total}\\ floor\\ area\) = the combined area of all floors in the building
• \(\text{lot}\\ area\) = the area of the land parcel

Step by step method

1. Find the total floor area by adding the area of each floor.
2. Find the lot area of the property.
3. Divide the total floor area by the lot area.
4. Compare the result with local zoning rules to see whether the project is allowed.

Worked example

Problem. A building has a total floor area of \(8{,}400\) square feet on a lot that is \(6{,}000\) square feet. Find the FAR.

1. Use the formula \( FAR = \frac{total\\ floor\\ area}{lot\\ area} \).
2. Substitute the values, \( FAR = \frac{8{,}400}{6{,}000} \).
3. Compute the quotient, \( FAR = 1.4 \).

Tips and common mistakes

• Make sure the lot area and floor area use the same unit before dividing.
• Do not confuse total floor area with building footprint, because FAR uses the sum of all floors, not just the ground floor.

Frequently asked questions