Floor area ratio (FAR) is a zoning metric calculated as total building floor area divided by lot area, used to determine the maximum permitted square footage that can be built on a given parcel. A FAR of 0.5 on a 100,000 square foot lot, for example, permits a maximum of 50,000 square feet of building floor area, though single-story industrial buildings often use a smaller portion of the theoretically available FAR than multi-story buildings would.
FAR calculation example
| Lot size | FAR limit | Maximum buildable floor area |
|---|---|---|
| 100,000 SF | 0.35 | 35,000 SF |
| 100,000 SF | 0.50 | 50,000 SF |
| 100,000 SF | 0.75 | 75,000 SF |
What to watch for before committing
FAR limit confirmation
Verify the specific FAR limit allowed under the property's zoning classification before assuming maximum buildable square footage.
Interaction with lot coverage and height limits
Understand that FAR works alongside lot coverage and height restrictions, and the most restrictive of the three ultimately caps your buildable area.
Existing building compliance
Confirm whether an existing building's square footage already complies with current FAR limits or holds non-conforming status.
Expansion feasibility calculation
Calculate remaining FAR capacity if you're evaluating potential building expansion.
Single-story vs multi-story implications
Recognize that industrial buildings, typically single-story, often don't approach maximum theoretical FAR the way multi-story buildings might.
Mezzanine and interior floor area counting
Confirm whether mezzanine or interior additional floor area counts toward FAR calculations under local rules.
When you need to know this
- Site selection for new construction — calculating maximum buildable square footage on a candidate parcel
- Planning building expansion — confirming remaining FAR capacity supports your intended addition
- Evaluating land purchase for development — determining a parcel's development potential based on FAR limits
- Adding mezzanine or interior floor area — verifying whether the addition counts toward FAR and remains within limits
Frequently asked questions
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