FAR Calculator — Floor Area Ratio & Max Buildable Area

    Calculate maximum allowable floor area based on lot size and FAR limits. Useful for quick zoning feasibility checks.

    Tips

    • FAR definitions vary — some areas exclude basements, parking, or mechanical spaces.
    • Bonuses and incentives can increase allowed area in some zones.
    • Treat this as a first-pass feasibility check, then confirm with the local zoning code.

    Planning tool only — zoning definitions and exclusions vary widely. Confirm FAR rules and floor area definitions with local planning regulations.

    Example Calculation

    A 10,000 sqft lot with a 0.5 FAR allows up to 5,000 sqft of total floor area. If your concept is 4,200 sqft, you're using about 84% of the allowed FAR.

    FAR Quick Examples

    Lot SizeFARMax Buildable Area
    5,0000.63,000
    7,5000.86,000
    10,0001.010,000
    12,0001.214,400
    20,0000.510,000

    Frequently Asked Questions

    What is FAR?

    FAR is the ratio of total building floor area to lot area.

    Does FAR equal building footprint?

    Not necessarily. FAR is total floor area across levels; footprint is just the ground-floor area.

    Do basements count toward FAR?

    Sometimes yes, sometimes no — it depends on the jurisdiction and definition of floor area.

    Is this calculator accurate for my city?

    It's a first-pass estimate. Always confirm your zone's rules with the local planning authority.

    What if my proposed area exceeds the limit?

    You may need to reduce floor area, adjust level count/footprint, or explore bonuses/incentives if applicable.

    Typical Results

    Single-family residential(typical suburban zoning)0.3–0.6 FAR
    Urban residential(higher density zoning)0.8–2.0 FAR
    Mixed-use / commercial(downtown zoning)2.0–6.0 FAR

    💡 FAR violations can block permits and require redesign — verify your local limit before designing.

    Common Mistakes

    • •Using building footprint instead of total floor area (multiply footprint by number of stories)
    • •Not knowing whether your jurisdiction excludes parking structures or basement from floor area
    • •Confusing FAR with lot coverage (which limits only the footprint, not total floor area)

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