Free Floor Area Ratio (FAR) Calculator

Calculate the floor area ratio for a building by dividing the total building floor area by the lot area, and determine the maximum buildable square footage under zoning limits.

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sq ft
sq ft

Current Floor Area Ratio

0.40

Maximum Building Area Allowed7,500
Remaining Buildable Area1,500
Average Floor Plate (footprint)3,000
Implied Lot Coverage20.0%
FAR Utilization80.0%

Current Floor Area Ratio vs Total Lot Area (sq ft)

View formula & how it works →

Floor Area Ratio (FAR)

FAR is a zoning measurement that compares the total floor area of a building to the area of the lot it sits on. It controls building bulk and is especially important in urban zoning.

Formula

FAR = Total Building Floor Area / Lot Area

For example, a 6,000 sq ft building on a 15,000 sq ft lot has a FAR of 0.40.

How FAR Controls Development

  • FAR of 0.25-0.50: Low-density residential (single-family)
  • FAR of 0.50-1.0: Medium-density residential (townhomes, duplexes)
  • FAR of 1.0-3.0: Mixed-use, multifamily, low-rise commercial
  • FAR of 3.0-10.0: Urban commercial, mid-rise to high-rise
  • FAR of 10.0+: Dense urban core (Manhattan-type development)

    • FAR vs. Lot Coverage

  • Lot coverage limits the footprint; FAR limits total floor area
  • A tall, narrow building can have a high FAR with low lot coverage
  • Both must be satisfied for zoning compliance

    • FAR Bonuses

    Many cities offer FAR bonuses for public plazas, affordable housing, LEED certification, or transit-oriented development.

    Example Calculation

    A 15,000 sq ft lot with a 2-story building totaling 6,000 sq ft, and a maximum allowed FAR of 0.50.

    1. 01Current FAR: 6,000 / 15,000 = 0.40
    2. 02Maximum allowed floor area: 15,000 x 0.50 = 7,500 sq ft
    3. 03Remaining buildable: 7,500 - 6,000 = 1,500 sq ft
    4. 04Average floor plate: 6,000 / 2 = 3,000 sq ft
    5. 05Implied lot coverage: 3,000 / 15,000 = 20.0%
    6. 06FAR utilization: 0.40 / 0.50 = 80.0%

    Frequently Asked Questions

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