Floor Area Ratio (FAR) Calculator

Calculate the ratio of total building floor area to the lot size, a key metric in zoning and urban density planning.

Plot & Building Data

Unit System

Total Built-up Area (sq ft)

ft²

Total Plot/Lot Area (sq ft)

ft²

Zoning Metrics

Checking compliance?

Enter the total area of all building floor levels and the total size of the lot to calculate the FAR.

Overview

Floor Area Ratio (FAR), also known as Floor Space Index (FSI), is the relationship between the total floor area of a building and the area of the land it sits on. It is the primary tool urban planners use to control building bulk, population density, and land-use intensity within a city.

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Pro Tips

Remember that 'Total Floor Area' includes every level of the building, not just the ground floor footprint.
If you know your local FAR limit, multiply it by your lot area to find the maximum building size you can legally build.
Always check local zoning ordinances for the 'Lot Coverage' limit, which is a separate rule governing the maximum building footprint.

Fun Facts

"A FAR of 1.0 means the total indoor space is exactly equal to the total land area."
"Density varies wildly: Manhattan's FAR can exceed 15.0, while suburban residential zones are often capped at 0.5 or 0.7."
"In many jurisdictions, basements, balconies, and mechanical rooms are 'exempt' and not counted toward the FAR."

Formula: FAR = Total Gross Floor Area / Lot Area

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