Floor Area Ratio (FAR) Calculator

FAR is total floor area divided by the lot size — a key zoning metric.

How the Math Works

The Floor Area Ratio (FAR) is calculated by dividing a building's total floor area by the area of the land it sits on. Total floor area includes every floor of the building, from the ground up, while lot area refers to the total square footage of the property, including any open spaces, parking, or landscaping. This results in a dimensionless ratio that quantifies how much of the land is covered by building space. For example, a building with 3,000 square feet of total floor area on a 2,000 square foot lot would have an FAR of 1.5.

Practical Applications

Architects and developers use FAR to ensure buildings comply with local zoning regulations, which often limit construction density. Before designing or building, professionals calculate FAR to determine maximum allowable building sizes and to plan multi-story structures that maximize usable space within legal constraints. This helps avoid costly redesigns or violations during the approval process.

Day-to-Day Use

Understanding FAR helps homeowners and renters gauge neighborhood density and development potential. A higher FAR indicates a more densely built area, which can affect property values, noise levels, and access to amenities. For city planners, FAR is a tool for managing urban growth and ensuring balanced development across different zones, ultimately shaping the character and livability of communities.

Worked example

3,000 ft² on 5,000 ft² → FAR 0.6.

FAQ