Pro-Rata Share: GLA vs. GLOA, Which Denominator Protects Tenants?
Your pro-rata share of CAM costs is a fraction: your square footage divided by a denominator representing the total area of the building or project. The denominator choice determines what percentage of the total expense pool you pay. In a building with significant vacancy, the difference between Gross Leasable Area (GLA) and Gross Leasable Occupied Area (GLOA) as the denominator can mean a 30%–60% swing in your annual CAM bill.
The ICSC explicitly identifies this as a tenant protection issue: "it would be incorrect to include" anchor GLA in the denominator when the anchor pays fixed or no CAM, because that inflates the allocable share for inline tenants.
What GLA and GLOA Mean
Gross Leasable Area (GLA) is the total measured floor area in a building that can be leased to tenants, regardless of whether it is currently occupied. BOMA's retail measurement standard (ANSI/BOMA Z65.5) defines GLA as a space classification for measuring floor area in retail buildings. Common areas are not included in GLA; they are separately maintained and the cost of maintaining them is what gets allocated among tenants based on their GLA.
Gross Leasable Occupied Area (GLOA) is the subset of GLA that is actually occupied. BOMA uses the phrase "occupied gross leasable area" in recognition criteria. In practical lease math, GLOA is derived by applying an occupancy filter to already-measured GLA.
The question in any CAM allocation is: does the denominator of the pro-rata fraction represent total GLA (including vacant spaces) or GLOA (occupied spaces only)?
GLA vs. GLOA: Formula Comparison Table
The same 5,000 SF tenant in the same 100,000 SF center faces dramatically different CAM outcomes depending on which denominator the lease uses.
| Method | Formula | Example Denominator | Tenant's Share | Annual CAM ($500K pool) | Overcharge Potential |
|---|---|---|---|---|---|
| GLA (full building) | Tenant SF / Total GLA | 100,000 SF | 5.0% | $25,000 | Baseline (tenant-favorable) |
| GLOA (occupied only, 60% occupied) | Tenant SF / Occupied GLA | 60,000 SF | 8.3% | $41,667 | +$16,667/year |
| GLA minus anchor (40,000 SF anchor excluded) | Tenant SF / (GLA - Anchor SF) | 60,000 SF | 8.3% | $41,667 | +$16,667/year |
| GLOA minus anchor (worst case for tenant) | Tenant SF / Occupied non-anchor SF | 36,000 SF | 13.9% | $69,444 | +$44,444/year |
Same building, same tenant, same CAM pool, 4 different results. The denominator in your lease determines which row applies to you.
Why the Denominator Choice Has Large Dollar Consequences
Scenario: A 100,000 SF shopping center. You lease 5,000 SF. CAM pool is $500,000.
| Denominator | Your Share | Your Annual CAM |
|---|---|---|
| GLA = 100,000 SF | 5% | $25,000 |
| GLOA = 60,000 SF (40% vacant) | 8.3% | $41,667 |
With a GLOA denominator at 40% vacancy, you pay $16,667 more per year, a 67% increase in your CAM burden. Over a 5-year lease, that's $83,333.
The landlord's preference is typically a GLOA denominator because it ensures the full CAM pool is recovered from occupied tenants. The tenant's preference is a GLA denominator because vacant space cost stays with the landlord.
Neither structure is inherently improper, the question is what the lease says and whether the denominator is clearly defined. Disputes arise when the lease uses an ambiguous term like "leasable area" without specifying whether vacant space is included.
The Anchor Exclusion Compound Problem
In retail shopping centers, the denominator issue is compounded by anchor exclusions. Anchor tenants, major department stores, grocery chains, big-box retailers, often pay a fixed CAM amount or maintain their own areas, with their square footage excluded from the pro-rata denominator.
From ICSC workshop materials: if a 40,000 SF anchor is excluded from a 100,000 SF center's denominator, inline tenants allocate costs based on 60,000 SF, not 100,000 SF.
Combined with building vacancy, the effect can be dramatic:
- 100,000 SF center
- 40,000 SF anchor excluded from denominator
- Remaining 60,000 SF at 70% occupancy = 42,000 SF GLOA
- Your 5,000 SF share: 5,000 ÷ 42,000 = 11.9%
Compare to: 5,000 ÷ 100,000 = 5% if full GLA (including anchor) were the denominator.
The difference: 11.9% versus 5% of the same $500,000 CAM pool = $59,500 versus $25,000. Your annual bill nearly triples.
NRTA's "CAM Wars" newsletter notes that anchors "pay a particular deal, one that usually is a gross deal and does not involve payment of CAM," so smaller tenants effectively subsidize any shortfall. The anchor exclusion is standard practice in shopping center leasing, but its interaction with the denominator definition is something many tenants don't notice until their first reconciliation.
What Published Case Law Shows
Denominator disputes produce published litigation. Three cases illustrate the recurring pattern:
Payless Shoesource, Inc. v. Joye (E.D. Cal. 2014): Classic parcelization dispute. The tenant's lease formula allocated CAM by the ratio of tenant premises floor area to "total gross leasable floor area of completed buildings within the Development." After the landlord sold portions of the property to different owners, the denominator changed. The court initially granted summary judgment for the landlord based on course-of-dealing, the parties had used the revised denominator for years without objection. The case was later vacated and settled, but it documents the basic dispute pattern and how course-of-dealing can lock in a methodology.
Accenture LLP v. CSDV-MN Limited Partnership (N.D. Ill. 2007): Dispute over whether a parking garage should be included in the building's "rentable area" denominator. The court held that including the garage would make the negotiated numeric percentage shares in the lease schedule inaccurate "at the outset," and excluded it. Specific language in the lease controlled over an expansive definition.
Sea Fare's American Café, Inc. v. Brick Market Place Associates (R.I. Sup. Ct.): Later courts have cited this case for the proposition that where a lease provides a specific numeric percentage share that would be wrong "at the outset" if a disputed area were included in the denominator, that structure supports construing the denominator to exclude the disputed area.
These cases share a common pattern: specific numeric commitments in the lease tend to control over general definitional language. Tenants who negotiate a fixed percentage share bypass the denominator dispute entirely, but they also lose the protection of a denominator that adjusts with building size changes.
The Denominator Options for Tenants
Option 1: Fixed GLA denominator (total leasable area)
"Tenant's pro-rata share shall equal the rentable square footage of the Premises divided by the total Gross Leasable Area of the Building, which the parties agree is [total SF] square feet. The GLA denominator shall not be reduced by vacant space, and shall not be increased or decreased without Tenant's written consent."
Best for: Tenants in buildings with moderate to low vacancy, or tenants whose primary concern is predictability.
Option 2: GLA denominator with anchor exclusion adjustment
"The denominator for purposes of calculating Tenant's pro-rata share shall be the total Gross Leasable Area of the Project, excluding the gross leasable area of any tenant that (a) pays a fixed CAM contribution not adjusted by pro-rata allocation, (b) maintains its own parcel, or (c) is specifically designated as an anchor tenant in Exhibit [X]. Any shortfall between an anchor tenant's fixed CAM payment and its pro-rata share shall be borne by Landlord and shall not be reallocated to other tenants."
Best for: Inline tenants in shopping centers with anchor tenants paying fixed CAM.
Option 3: Minimum denominator protection
"In no event shall the denominator used to calculate Tenant's pro-rata share be less than [X]% of the total Gross Leasable Area of the Building. If actual occupancy falls below this threshold, the denominator shall be calculated as if [X]% of the GLA were occupied."
Best for: Tenants in buildings with persistent vacancy risk.
How to Identify Your Current Denominator
Review your lease for the definition of "pro-rata share," "tenant's share," or "tenant's proportionate share." Look specifically for:
- Whether the denominator is described as total "leasable," "rentable," or "occupied" area
- Whether the denominator includes or excludes anchor space
- Whether the denominator is a fixed number stated in the lease or a floating calculation
- Whether the denominator adjusts for building expansions or sales of parcels
If the denominator is undefined or uses "leasable" without specifying whether vacant space is included, the provision is ambiguous. In that case, the landlord's methodology (whatever has been applied consistently) may become binding as a matter of course of dealing, particularly in jurisdictions like New York with a 6-year statute of limitations under CPLR § 213, where years of unchallenged billings can establish the operative methodology.
What tenants ask about pro-rata share denominators
What is the most common denominator in retail leases?
Retail leases most commonly use a total GLA denominator based on the shopping center or project, because BOMA's retail standard defines GLA as the measure for allocating shared common area costs. However, anchor exclusions from the denominator are also standard, meaning the effective denominator is total GLA minus anchor GLA, not total GLA of the entire center.
Is a GLOA denominator ever appropriate?
Some practitioners argue that a GLOA denominator is appropriate because it ensures the landlord recovers the full CAM pool from current occupants rather than carrying a loss on vacant space. From a landlord's perspective, it prevents underrecovery. From a tenant's perspective, it creates cost exposure that fluctuates with the landlord's leasing success. The right answer depends on vacancy risk in the specific building and the relative bargaining positions of the parties.
What if the lease uses "rentable area" instead of "leasable area"?
Office leases typically use rentable area, which is a different calculation. Under BOMA's office standard, rentable area includes a load factor for shared areas, so the tenant's numerator and denominator both reflect rentable (not just usable) square footage. The denominator dispute in office leases often involves whether specific areas like parking garages or mechanical spaces count as rentable area, as in the Accenture case above.
Can the denominator change during my lease term?
Yes, without explicit protection. If the building expands, the landlord might add square footage to the denominator, reducing your percentage share (beneficial). If the landlord sells a parcel, the denominator might shrink, increasing your percentage share (harmful). A fixed denominator protects against both: your percentage share stays constant regardless of what happens to the rest of the building.
What is the statute of limitations on challenging a pro-rata share calculation?
It varies by state. California: 4 years (CCP § 337). Texas: 4 years (Tex. Civ. Prac. & Rem. Code § 16.004). New York: 6 years (CPLR § 213). Illinois: 10 years for written contracts (735 ILCS 5/13-206). Courts generally measure the limitations period from when the methodology was first applied and the tenant had the information needed to challenge it, not from a later audit.
Legal Disclaimer: This article provides general educational information about pro-rata share provisions in commercial leases. Case citations and examples are for educational purposes. This is not legal advice. Consult qualified commercial real estate counsel before negotiating or signing any commercial lease.
Related reading:
- The Commercial Tenant's Guide to CAM Lease Language, complete provision-by-provision guide
- What Is a Gross-Up Clause in a Commercial Lease?
- What Is an Anchor Exclusion in a CAM Lease?
- CAM Exclusions Every Commercial Lease Should Have
Frequently Asked Questions
What is the difference between GLA and GLOA in CAM calculations?
GLA (Gross Leasable Area) is the total rentable square footage of all spaces in a property, occupied or vacant. GLOA (Gross Leasable Occupied Area) includes only occupied spaces. When the denominator is GLOA, each occupied tenant's share increases as vacancy rises. When it is GLA, the landlord absorbs the cost of vacant space rather than passing it to remaining tenants.
Which pro-rata denominator is better for tenants, GLA or GLOA?
GLA is generally better for tenants. With GLA as the denominator, your share of the CAM pool stays constant regardless of how many other tenants are in the building. With GLOA, if a large tenant vacates, your percentage and your bill go up even though nothing changed about your space or your lease.
Can a landlord switch from GLA to GLOA during my lease?
Only if the lease explicitly permits it. If your lease defines the denominator as total gross leasable area of the property, the landlord cannot switch to occupied area without a lease amendment. Any unauthorized denominator change is a CAM overcharge equal to the difference between your share under each methodology.
Why does anchor tenant square footage matter for pro-rata share?
If an anchor tenant is excluded from the CAM pool but their square footage remains in the denominator, inline tenants pay a lower share than they would under a pure GLOA calculation, but the anchor is still not contributing to costs. The ICSC specifically flags this as an error when anchor square footage inflates the denominator but anchor contributions do not reduce the pool.
How do I calculate my correct pro-rata share?
Divide your rentable square footage by the denominator defined in your lease, whether GLA, GLOA, or a defined subset. Multiply the resulting percentage by the total billable CAM pool. Compare this to what the landlord billed. If the landlord used a different denominator or a smaller total area, the difference is the overcharge.