NNN Lease Calculator: Pro-Rata and Occupancy Cost

A triple net (NNN) lease bills base rent and, on top of it, the tenant’s share of recoverable property taxes, building insurance and maintenance. This calculator turns the areas and the building-level expense totals you enter into that share and the resulting occupancy cost. It does not look up rents, taxes or CAM, and it ships with empty inputs so nothing on the screen can be mistaken for a market rate.

Pro-rata share

NAIOP’s Commercial Real Estate Terms and Definitions (2024) defines pro rata expense share as “the percentage that a tenant pays of reimbursable expenses; usually, but not always, calculated by dividing the net rentable area of a tenant’s leased premises by the net rentable area of the building.” NAIOP says the share is “usually, but not always” calculated this way and that expense stops and other lease terms impact the calculation, so confirm both the numerator and the denominator in the lease. A smaller denominator would give a larger percentage. This tool uses that usual formula and nothing else. If your lease uses a different denominator, the percentage here will be wrong.

The three nets, plus an optional management fee

Property tax, building insurance and CAM are entered as annual building totals, then multiplied by the share. That matches how a landlord’s operating-expense statement is written. Do not type a per-square-foot CAM quote into those fields.

The management-fee field is optional. Link Logistics lists property management fees among typical industrial CAM charges; Prologis, in its 2025 Form 10-K, includes the cost of property-management personnel among rental expenses, and states that generally the majority of those rental expenses are recovered from customers. If your statement already folds the fee into CAM, leave the field on “not separate.” If it is shown on its own, enter it as a percent of tax + insurance + CAM or as a building-level annual dollar amount. Either way, the tenant pays the pro-rata slice, not the whole building figure. That treatment is this calculator’s arithmetic, not a claim that every lease computes the fee that way.

Base rent period

Check whether a quoted rate is per year or per month; the toggle below handles both. A monthly figure looks dramatically smaller if you read it as annual. The occupancy totals are always shown annual and monthly.

What this number is not

Link Logistics says CAM is typically reconciled annually against actual expenses, with the tenant paying estimated CAM charges through the year; whether your taxes and insurance work the same way is set by the lease. This tool has no true-up step: it reports the share of the totals you typed.

Occupancy cost here is base rent plus NNN. It does not include utilities billed in your own name, your insurance programme, payroll, racking, or restoration. For that wider list see True Cost of Warehouse Space and the opening-cost guide. Next, compare it with a 3PL in the 3PL vs lease calculator. Defined terms: NNN, CAM, pro-rata share, CAM reconciliation.