🏢 Floor Area Ratio (FAR) Calculator
Work out the floor area ratio (FAR) of a building project and see how much more floor area local zoning would still allow.
What is Floor Area Ratio?
Floor Area Ratio (FAR) compares the total floor area of a building to the size of the lot it sits on. Zoning codes use FAR to control building density and overall bulk on a parcel of land.
The Formula
FAR = Total Building Floor Area ÷ Lot Area. For example, a 20,000 sq ft building on a 10,000 sq ft lot has a FAR of 2.0. Most jurisdictions set a maximum allowed FAR by zoning district, which caps how much total floor space (across all stories) can be built.
This calculator also shows the maximum floor area your lot could support under a given allowed FAR, and how much additional floor area remains available.
Zoning definitions of FAR vary by city and may exclude basements, parking, or mechanical space — always confirm exact rules with your local planning department before relying on this for a real project.