Last updated: September 27, 2026
Which floor area determines commercial rent?
The lease's agreed measurement definition determines the area used for rent. Gross building area, internal area, retail gross leasable area, and office rentable area describe different things. In BOMA retail measurement, tenant GLA does not include an allocation of common areas; common-area expenses are a separate issue. Always identify the standard and edition behind the number.
Five terms that should not be used interchangeably
A building can have several valid area figures because each answers a different question. Planning authorities may need one measurement, construction teams another, and leasing teams another. Definitions also vary by country, local rules, and measurement standard. The following is a terminology guide, not a substitute for the applicable measurement document.
Commercial floor area terminology and context
Term Abbreviation General meaning Important qualification
Gross floor area GFA An aggregate building-area measure used in planning, development, or property reporting. Boundaries and exclusions depend on the applicable definition or local code. Gross internal area GIA Under the RICS convention, area measured to the internal face of perimeter walls at each floor. It includes service and circulation areas; it is not simply tenant working space. Net internal area NIA Under the RICS convention, usable internal area after specified exclusions. Apply the detailed rules for circulation, services, structural features, and other exclusions. Gross leasable area GLA A tenant-area measure commonly encountered in retail leasing. Under BOMA retail guidance, it excludes an allocation of common areas. Net leasable area NLA A leasable-area term used in some markets and documents. Check its actual definition; it is not a universal synonym for BOMA office rentable area.
For the internal-area conventions, consult the RICS Code of Measuring Practice . For retail treatment, see BOMA's measurement guidance . Do not apply one convention's exclusions to a figure prepared under another.
Gross floor area is not automatically the rentable area
Gross area can help explain the overall scale of a property, but it does not establish the area occupied by each tenant. A total made by multiplying one floor's footprint by the number of floors is only appropriate when those floors and the governing definition support that calculation. Setbacks, voids, mezzanines, and different floor plates can change the result.
When comparing buildings, record the unit of measurement and basis alongside the number. “50,000 square feet” is less useful than a figure labeled with its purpose, measurement method, and date. The same discipline helps prevent mismatches between brochures, valuation assumptions, plans, and lease schedules.
Retail GLA and common-area expenses
A retail tenant can pay expenses associated with common areas without those areas being added to its GLA. Distinguish the physical area used to calculate base rent from the formula used to allocate common-area maintenance or other operating expenses. Read both provisions: the expense allocation might use a different denominator, exclusions, caps, or negotiated terms.
Likewise, do not assume a single-tenant property's GLA must equal a particular gross building measure. The label alone does not resolve which walls, ancillary areas, or other features the selected standard includes.
GLA calculation: add consistently measured spaces
Assume three non-overlapping retail spaces have already been measured as 2,000, 3,000 and 5,000 sq ft of GLA under the same stated convention. Their combined GLA is 2,000 + 3,000 + 5,000 = 10,000 sq ft . This is an aggregation of measured areas, not a universal formula for subtracting common space from gross building area. Confirm the measurement basis and avoid double counting. Read our GLA definition and example .
Office usable area and rentable area
Office rent quotations commonly distinguish the space attributable to an occupant from rentable area after applicable allocations. Ask whether the quoted figure is usable, occupant, or rentable area and request the schedule that connects them. Our BOMA standards guide explains the office methods and the importance of naming the edition.
The area needed for a business layout and the area used for charging rent are related but different questions. A larger lobby may serve the property well even though it does not fit additional desks inside a suite. Compare the full occupancy cost with the space and amenities the business needs.
Core factor and tenant share: a corrected example
“Core factor” is used inconsistently. This simplified example separates a tenant's proportion of the building's usable area from the rentable-to-usable multiplier . It illustrates arithmetic, not a complete BOMA measurement procedure.
Assume a building has 50,000 square feet of tenant usable area and 10,000 square feet of allocable common area. Your suite occupies 10,000 usable square feet. Under the example's proportional allocation:
Tenant share: 10,000 ÷ 50,000 = 20% .
Common area allocated to the suite: 20% × 10,000 = 2,000 square feet .
Illustrative rentable area: 10,000 + 2,000 = 12,000 square feet .
Rentable-to-usable multiplier: 12,000 ÷ 10,000 = 1.20 , a 20% add-on .
Annual base rent at $28 per rentable square foot: 12,000 × $28 = $336,000 .
The allocation adds $56,000 to annual base rent compared with charging $28 on the suite's 10,000 usable square feet. The tenant share and add-on both happen to be 20% here. A tenant occupying 5,000 usable square feet in the same example would have a 10% tenant share but the same 1.20 multiplier. A tenant's 100% share of an entire building likewise does not establish a 100% load-factor add-on.
Make the numbers clear in the lease and the listing
Identify the measurement standard and edition, rather than relying only on an acronym.
List the measured suite area, rentable area where applicable, and allocation method separately.
Show whether the rent rate is monthly or annual and which area it multiplies.
Explain operating-expense obligations separately from base rent.
Resolve conflicting figures before signing or publishing the property materials.
For land leased separately from a building, read what a ground lease means . To present consistent property information in brochures and listings, explore commercial real estate software from CREOP and see examples .
Frequently asked questions
What is the difference between GLA and NLA?
GLA and NLA are leasable-area terms whose definitions depend on the market and measurement convention. BOMA retail GLA excludes an allocation of common areas. Do not assume either term is interchangeable with office rentable area.
What is gross floor area?
Gross floor area is an aggregate building-area measure used for purposes such as planning or development. Its boundaries and exclusions depend on the applicable definition or local rules; it is not automatically the area used to charge rent.
Is a tenant's proportional share the same as a load factor?
No. A tenant's share is a fraction of the relevant building area. A rentable-to-usable multiplier compares the tenant's rentable and usable areas. The two calculations can produce different percentages, even though both happen to be 20% in the worked example.
Do tenants pay for common areas?
A lease can allocate common-area expenses to a tenant. Office measurement can also allocate area when calculating rentable space. These are separate mechanisms; a retail common-area expense charge does not mean common space is included in tenant GLA.