Free Tool: Calculator

Pro Rata Share Calculator

Enter your tenant square footage, the building denominator, and your landlord's stated percentage to verify the math instantly and catch one of the most common CAM overcharge sources.

How pro-rata share works: Your share of CAM expenses equals your leased square footage divided by the total denominator area defined in your lease. If the landlord uses the wrong denominator, your share is inflated and you overpay.

Your Lease Details

Your Tenant RSF (sq ft)

Building Denominator RSF (sq ft)

Landlord's Stated Pro-Rata %

Total Allocable CAM Expenses ($)

Pro-Rata Share Analysis

Enter your details above to see your pro-rata analysis.

How pro-rata share errors happen

Pro-rata share errors are the second most common CAM overcharge category. The most frequent source is a denominator that is smaller than your lease specifies. A smaller denominator inflates your percentage and increases your share of every expense in the pool.

Common causes: anchor tenant square footage excluded from the denominator without a matching pool reduction; landlord using occupied area instead of total leasable area during vacancy periods; or outdated building RSF records that do not reflect the current building size.

Enter your tenant RSF, the denominator RSF from your lease, and your landlord's stated percentage to verify the math and estimate any annual overcharge.

Frequently Asked Questions

What is pro-rata share in a commercial lease?

Pro-rata share is the percentage of building operating expenses a tenant is responsible for, calculated as the tenant’s rentable square feet divided by the total denominator square feet defined in the lease. A 5,000 SF tenant in a 50,000 SF building has a 10% pro-rata share.

What is the denominator in a pro-rata share calculation?

The denominator is the total square footage used to divide operating expenses. Your lease defines whether the denominator is total leasable area, occupied area, or a defined building RSF. Using the wrong denominator is one of the most common CAM overcharge sources.

How do I check if my landlord’s pro-rata share is correct?

Divide your tenant RSF by the denominator RSF from your lease. Compare the result to the percentage on your CAM statement. A difference of more than 0.1% on a large expense pool creates a significant annual overcharge.

What is an anchor exclusion in pro-rata share?

Anchor tenants in retail properties sometimes negotiate to be excluded from the denominator. This increases remaining tenants’ shares. The exclusion should be matched by a corresponding reduction of anchor-related expenses from the CAM pool. When the exclusion is applied without the matching pool reduction, smaller tenants pay more than their fair share.

What if my calculator result shows my landlord is using the wrong denominator?

A wrong denominator inflates every tenant’s share, sometimes by 20% or more, and the error compounds every year. Once you have identified the discrepancy, you will need your actual lease, the landlord’s occupancy report, and documentation of the actual GLA to build a dispute. CAMAudit’s Pro-Rata Share Error rule analyzes your lease documents and reconciliation together, calculates the correct share, and quantifies the exact overcharge amount for your dispute letter draft.

Next Best Step

Verify your pro-rata share against your lease

A wrong square footage or incorrect denominator inflates every CAM charge for the full lease term.

CAM overcharge guide

See how pro-rata share errors rank among the most common CAM violations.

See a sample report

Preview how pro-rata share findings are documented in the audit.

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How pro-rata share errors happen

Enter your tenant RSF, the denominator RSF from your lease, and your landlord's stated percentage to verify the math and estimate any annual overcharge.