The fraction of total building operating expenses allocated to a specific tenant, calculated as the tenant's rentable square footage divided by the total rentable area of the building or project.
Pro-rata share determines how much of the building's shared costs — taxes, insurance, maintenance, management — each tenant pays. For example, a tenant occupying 5,000 of a 50,000 square foot building has a 10% pro-rata share. The denominator matters: if the landlord uses gross building area rather than occupied space, tenants may pay for vacant space. Some leases use a "project" denominator that includes multiple buildings, which can increase costs. Tenants should audit the denominator annually and confirm it matches the lease definition, particularly after expansions, contractions, or new tenants joining the building. Property managers automating CAM reconciliation can use CapVeri.com to verify pro-rata share calculations automatically across every tenant in their portfolio, ensuring each annual reconciliation uses the denominator specified in the lease. CamAudit.io includes a pro-rata share error detection rule that cross-references the denominator in your lease against what the landlord used in the reconciliation statement.
Lextract extracts these fields directly from your lease PDF:
Pro-rata share is calculated by dividing the tenant's rentable square footage (RSF) by the total rentable square footage of the building or property. For example, a tenant leasing 5,000 RSF in a 50,000 RSF building has a 10% pro-rata share. This percentage is applied to shared costs including CAM charges, property taxes, insurance premiums, and other operating expenses that are allocated among tenants proportionally based on the space they occupy.
The pro-rata share applies to all costs that are allocated among tenants based on their proportionate occupancy, including common area maintenance (CAM), real estate taxes, building insurance, shared utilities, property management fees, and other operating expenses. In a NNN lease, the pro-rata share determines the tenant's contribution to each of these expense categories separately. In a modified gross lease, the pro-rata share determines how much of any operating expense increase above the base year or expense stop the tenant owes.
The denominator (total building RSF) directly affects how much each tenant pays. A larger denominator means each tenant pays a smaller percentage of shared costs. If a building measures 50,000 RSF total, a 5,000 RSF tenant pays 10%. But if the landlord uses 45,000 RSF (excluding vacant suites), the same tenant pays 11.1% — an 11% increase in expense obligations. Tenants should verify that the denominator includes all rentable square footage in the building, including vacant spaces, to prevent their pro-rata share from increasing as neighboring tenants vacate.
A practical 15-point checklist covering every major negotiation lever in a commercial lease — from base rent and TI to CAM caps, renewal options, and exit rights.
Lease renewal is your best negotiating opportunity as a tenant. Learn when to start, what to ask for, and how to use market data to lower your rent and improve terms.
The five main types of commercial leases — NNN, gross, modified gross, percentage, and ground — have very different cost structures and risk profiles. Here's how each works.
Need CAM recovery under your brand?
CAMAudit gives firms white-label CAM recovery infrastructure while they keep the client relationship and deliver branded reports.
Explore the partner program →Upload a commercial lease PDF and get 126 structured fields — including all the terms defined in this glossary — extracted in minutes. $15 per lease.
Try It Free — No Signup Required