How is pro-rata share typically calculated?

Pro-rata share equals your rentable square footage divided by the total rentable square footage of the building. For example, if you lease 5,000 sqft in a 100,000 sqft building, your pro-rata share is 5%. This percentage is then applied to the total operating expenses to determine your share.

What happens if the building is partially vacant?

The denominator should always be the total rentable area of the building, regardless of vacancy. If the landlord uses only the occupied square footage as the denominator, existing tenants end up paying a larger share than their lease intended. This is a common error and a frequent source of overcharges.

Can CAMAudit verify my pro-rata share calculation?

Yes. CAMAudit's Rule 4 (Pro-Rata Share Error) recalculates your share from the square footage figures in your lease and compares it to the percentage applied on the reconciliation statement. Any discrepancy is flagged with the exact dollar impact.

Pro-Rata Share Definition Clause

Last updated: April 2026

By Angel Campa, Founder

Your pro-rata share multiplies against every CAM charge, so even a 0.5% error can cost thousands annually across the full expense pool.

What Is a Pro-Rata Share Definition Clause?

The pro-rata share clause defines the fraction of total building operating expenses that a tenant is responsible for paying. It is typically calculated by dividing the tenant's rentable square footage by the total rentable square footage of the building. This seemingly simple fraction is one of the most consequential numbers in any commercial lease.

Why This Clause Matters for CAM Audits

Even a small error in the pro-rata share calculation can compound into thousands of dollars over the lease term. Landlords sometimes use inconsistent square footage measurements, exclude vacant space from the denominator (inflating each tenant's share), or fail to update the share when the building is remeasured. Because this percentage multiplies against every CAM charge, getting it wrong affects every dollar you pay.

Sample Lease Language

“Tenant's Pro-Rata Share shall be calculated by dividing the total rentable square footage of the Premises (agreed to be 5,000 square feet) by the total rentable square footage of the Building (agreed to be 100,000 square feet), resulting in a Pro-Rata Share of five percent (5.00%). The total rentable square footage of the Building shall remain constant regardless of vacancy. If the Building is remeasured, the Pro-Rata Share shall be adjusted prospectively, and Landlord shall provide Tenant with written notice and supporting documentation.”

This is illustrative language only. Your actual lease language controls your rights.

Red Flags to Watch

⚠Pro-rata share is stated as a fixed percentage without showing the underlying square footage calculation
⚠Denominator excludes vacant or unleased space, inflating each tenant's share
⚠Lease does not specify the measurement standard (BOMA, ANSI, etc.)
⚠No provision for adjustment if the building is remeasured or reconfigured
⚠Different measurement methods are used for numerator and denominator

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Negotiation Tips

✓Require the lease to state both the numerator and denominator square footage, not just the resulting percentage
✓Specify that the denominator is the total rentable area of the building regardless of occupancy
✓Reference a specific measurement standard (BOMA 2017 or similar) for consistency
✓Include a right to verify the building's total square footage independently

Key Data

10-15%
An estimated 10-15% of commercial leases contain pro-rata share calculation discrepancies [industry estimate]
Source: Lease Audit Industry Reports (2024)

Explore Other Lease Clauses

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Pro-Rata Share: GLA vs. GLOA for Tenant Protection

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What Is Pro-Rata Share in a Commercial Lease? [2026 Guide]

CAM OverchargesGuide

Pro-Rata Share Errors: The Denominator That Costs Thousands

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Related Resources

Detection RulePro-Rata Share Error Detection RuleGross-Up Violation CAM Line ItemProperty Taxes (Pro-Rata)CAM Line ItemCommon Area Insurance Lease TypeTriple Net Lease (NNN)

Frequently asked questions

Need to extract lease terms before your audit?

A CAM audit is only as accurate as your lease data. lextract.io extracts 126 structured fields from any commercial lease PDF: CAM definitions, pro-rata share, caps, base year, and audit rights. So you have the exact terms your landlord is supposed to follow.

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This page provides general educational information. It is not legal advice and may not reflect the most current law in your state. Consult a licensed attorney for advice specific to your situation.