Floor Area Ratio (FAR) Calculator
Calculate municipal zoning Floor Area Ratio (FAR), total allowable gross floor area (GFA), and building footprint density.
Enter Calculation Inputs
Fill in the fields below. Instant client-side computation runs automatically in your browser as you type.
Common Searches & Natural Queries
What is the Floor Area Ratio (FAR)?
Floor Area Ratio (FAR) is the premier metric used by city planners and municipal zoning boards to regulate development bulk and urban density. It represents the proportion between the total usable floor area of all building stories combined and the total geographic area of the parcel.
Mathematical Formula & Methodology
The mathematical model underlying this tool operates on the following verified equation:
FAR = Gross Floor Area (GFA) / Total Lot Area; Max Allowable GFA = Lot Area à Max Zoning FAR
Understanding the Parameters:
- Total Parcel / Lot Area (measured in sq ft) â Primary input variable.
- Proposed Gross Floor Area (All Stories) (measured in sq ft) â Primary input variable.
- Maximum Permitted FAR by Zoning Code â Primary input variable.
How to Use This Calculator
Input your parcel size, the total aggregate building square footage across all floors, and the municipal zoning code maximum FAR threshold. View current density and zoning compliance status.
Worked Numerical Example
A lot measuring 10,000 sq ft with a proposed multi-story building of 25,000 sq ft gross floor area: FAR = 25,000 / 10,000 = 2.5. With a zoning cap of 3.0, the proposed structure is code-compliant and has 5,000 sq ft of remaining buildable capacity.
Key Considerations & Standards
Zoning definitions vary: many jurisdictions exclude underground basement parking, mechanical equipment rooms, and open balconies from gross floor area (GFA) tallies.
Frequently Asked Questions
Can a one-story building have a high FAR?
No. A one-story building covering 100% of the lot has an FAR of 1.0. To achieve an FAR of 4.0, a building must have at least 4 floors covering the full lot, or 8 floors covering 50% of the lot.
What is the difference between lot coverage and FAR?
Lot coverage measures only the horizontal building footprint on the ground relative to the lot size, whereas FAR measures the cumulative square footage of all vertical stories.