Gross floor area (GFA) is the total floor area of a building, measured to the outside face of its exterior walls and summed across every floor.
GFA is the full form of the abbreviation, and it is one of the most common inputs in zoning, development finance, and parking planning. It counts nearly everything inside the building envelope: tenant space, corridors, lobbies, stairs, restrooms, and mechanical rooms.
How GFA is measured
The basic rule is consistent, but the details are not. Jurisdictions differ on whether basements, mechanical penthouses, and structured parking count toward GFA, and many zoning codes exclude parking area when calculating floor area ratio (FAR). Always confirm which definition a code, lease, or appraisal is using before comparing numbers.
Why GFA matters for parking
Parking requirements and demand estimates are usually written as spaces per 1,000 square feet, and the basis matters. Office, industrial, and single-tenant buildings are usually measured against GFA, while retail and multi-tenant buildings are usually measured against gross leasable area (GLA), which is smaller. On an illustrative 100,000-square-foot building with 85,000 square feet of leasable space, a ratio of 4 per 1,000 produces 400 spaces on GFA but 340 on GLA. Misreading the basis changes the garage by 60 spaces, which at a $33,300 median cost per space is roughly $2 million.
Related terms: Gross Leasable Area (GLA), Parking Minimums, Fees-in-Lieu