GLOSSARY

Gross Floor Area (GFA)

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.

At a glance
Full form
GFA: gross floor area
Used in
Zoning, floor area ratio, parking ratios, development finance
Key fact
At 4 per 1,000 sq ft, 100,000 sq ft of GFA needs 400 spaces; 85,000 sq ft of GLA needs 340
SAME BUILDING, TWO BASES: GFA VERSUS GLAtenant spacetenant spacetenant spacetenant spacecorridors, lobby, stairs, mechanicalOuter line = GFA 100,000 sfTenant boxes = GLA 85,000 sfAt 4 spaces per 1,000 sfon GFA: 400 spaceson GLA: 340 spacesDifference: 60 spacesabout $2 million at the$33,300 median cost per space
The same illustrative building measured two ways. Gross floor area counts everything inside the walls; gross leasable area counts only tenant space. Applying a ratio to the wrong basis changes the garage.

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.

Try it
Same floor, three different areas

Pick a measure to see which parts of one office floor it counts, then see what that does to a parking requirement.

On an illustrative 10,000 sq ft office floor: gross floor area counts everything inside the exterior walls (10,000 sq ft); rentable area drops the stairs, elevators and shafts (9,200 sq ft); usable or leasable area counts only the tenant suites (8,000 sq ft). At 3 spaces per 1,000 sq ft, a 100,000 sq ft building needs 300 spaces on GFA but 240 on usable area.

Illustrative floor and shares (rentable 92%, usable 80% of GFA). Measurement rules and parking ratios come from your local code and lease standard; many codes also leave structured parking out of GFA when they calculate floor area ratio.

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