Commercial Lease Terms Explained: What CAM, NNN and Occupancy Cost Mean

A commercial lease prices space in layers: a base rent, plus a share of the building’s operating costs, plus whatever else the lease assigns to the tenant — and the label on the lease tells you which layers are yours. Under a triple net (NNN) lease the tenant pays base rent plus property taxes, insurance and common area maintenance (CAM); under a gross lease the landlord folds those into one rent figure; a modified gross lease sits between the two. "Occupancy cost" is the term for the whole stack added together, and it is the number every published rent benchmark is really about.

The single most useful thing on this page is that "occupancy cost" does not have one definition. Reputable sources disagree about what goes in it — the National Restaurant Association leaves CAM unnamed, restaurant accountants The Fork CPAs put CAM squarely inside, and a National Association of Realtors worked example counts utilities and maintenance too. Every term below is defined from a named source you can open, with the detail that changes what the number means.

What is occupancy cost in a commercial lease?

Occupancy cost is the total annual cost of holding the space, not just the rent — and its exact boundary depends on who is publishing the figure. As the National Association of Realtors puts it in a 2026 commercial valuation piece, "total occupancy costs extend beyond base rent or debt service," and it is those additional costs, the expenses over base, that "represent the true economic burden and must be fully considered when comparing alternatives."

Three sources, three different lines:

• The National Restaurant Association’s 2025 Restaurant Operations Survey instrument defines it as "Rent, taxes and property insurance are occupancy costs. These are sometimes called ‘fixed charges,’ since they usually are determined by the financial setup of the restaurant and usually not by the trend of its business." CAM is not named. Utility services, repairs and maintenance, and depreciation are separate line items on the same form.
• The Fork CPAs, restaurant accountants, define it as "base rent + percentage rent + CAM + property and real estate taxes + insurance, all divided by sales," and say it "does NOT include expenses like utilities and depreciation." CAM is in; utilities are out.
• NetSuite describes total occupancy cost as "rent or mortgage plus associated property taxes, fees and insurance."

And the National Association of Realtors example goes further still: its occupancy-cost table for a leased industrial building adds base rent, real estate taxes, utilities, property insurance, interior repairs and maintenance, and lawn and snow care to reach one total. Utilities are inside that number and outside The Fork CPAs’ version of it. Neither is wrong; they are answering slightly different questions. Before you use any occupancy percentage, find out what is in the numerator.

Why do two rent benchmarks that look comparable give opposite answers?

Because a percentage benchmark can be quoted on a rent-only basis or an all-in basis, and the two are not interchangeable. A rent-only figure counts base rent alone. An all-in figure counts base rent plus the taxes, insurance and CAM the lease passes through. Measure a base-rent-only lease quote against an all-in benchmark and the space looks comfortably affordable when it is not; measure it the other way and a workable deal looks impossible.

Two of our own guides show the difference concretely. The restaurant occupancy-cost benchmark is quoted all in, at roughly 5% to 10% of sales. The laundromat rent benchmark is quoted on rent alone, at 20% to 25% of gross sales. Those two numbers cannot be divided into each other to produce a multiple, because they are not measuring the same thing — and the tempting comparison is exactly the mistake this distinction exists to prevent. The same care applies to the coffee shop and fast casual figures, which read off the same all-in food-service data.

The practical habit is small: whenever a percentage appears, write down next to it whether it is rent-only or all-in, and convert your own lease to match before comparing.

What is base rent?

Base rent is the fixed rent for the space itself, before any operating expenses, taxes, insurance or percentage rent are added. It is the figure a listing advertises, usually as an annual dollar amount per square foot.

Cornell Law School’s Legal Information Institute frames every net lease against it: a net lease is one "in which the tenant pays the base rent plus some or all of the property’s operating and maintenance expenses." Base rent is therefore the smallest of the numbers you will end up paying, and the one most likely to be quoted at you on its own.

The gap is not trivial. In the National Association of Realtors restaurant example, base rent of $30.00 per square foot sits alongside $12.00 per square foot of triple net operating costs — a real occupancy cost of $42.00 per square foot, 40% above the advertised figure.

What is CAM in a commercial lease?

CAM stands for common area maintenance: the tenant’s share of the cost of running the parts of a property nobody leases exclusively. The Institute of Real Estate Management describes the everyday version as the shared elements of a shopping centre "unrelated to an individual store, like outdoor lighting, green space and parking."

CAM is billed as an estimate and trued up later, which is where it surprises first-time tenants. In IREM’s description, "throughout the year, tenants pay property owners estimated CAM charges based on projected expenses for these shared amenities. At yearend, property managers reconcile those estimates against actual costs." If actual costs ran above the estimate, the difference arrives as a bill you did not budget for.

IREM is also blunt about why CAM cannot be read off a rule of thumb: "No two leases are alike. Expense inclusions, exclusions, caps, and allocation methods can vary widely within the same property." Ask for the actual CAM history for the specific space, and ask whether the lease caps annual increases.

What does triple net or NNN mean?

A triple net lease is one where the tenant pays base rent plus the property’s taxes, insurance and maintenance. Cornell Law School’s Legal Information Institute defines it as "normally a commercial lease where the lessee pays rent and utilities as well as three other types of property expenses: insurance, maintenance, and taxes" — the three nets that give NNN its name.

It sits at the end of a series. The same source sets out the ladder: a single net lease is base rent plus property taxes; a double net lease adds insurance; a triple net lease is "rent + property taxes + insurance + CAM charges (and sometimes other costs such as utilities or repairs)." Note the hedge in that last clause — even the label does not fix the contents precisely, which is why the lease document beats the acronym every time.

Triple net is the normal structure for the businesses this site is written for. The National Association of Realtors notes that triple net leases "are the most landlord-friendly and are most common with restaurants and retail locations," and that they are typically long-term — Cornell puts the most common lengths at 10 or 15 years. A tenant on a NNN lease also absorbs the increases: unforeseen maintenance costs and tax rises land on you unless the lease caps them.

What is a gross lease, and what is a modified gross lease?

A gross lease is one where the tenant pays a single set rent and the landlord covers the property expenses out of it. Cornell’s Legal Information Institute defines it as a lease "where the tenant pays a set amount periodically for renting the property," in contrast with net leases "whose prices vary depending on expenses and factors such as the costs of maintenance, taxes, insurance, or market changes."

The trade-off is predictability for price: "This may result in higher rent for the lessee, but it also reduces their liability for changing prices." A gross rent that looks expensive per square foot against a NNN quote may be the cheaper deal once the NNN extras are added in.

A modified gross lease is the middle ground, and the National Association of Realtors describes it as "a compromise of the full-service lease and the net lease. A tenant might pay for their portion of their property taxes, property insurance, and CAMS, but they pay it as a lump sum payment along with their rent." Cornell notes a related hybrid: some gross leases provide "that the tenant will pay a higher rent if the landlord incurs a certain level of expenses called the ‘stop level.’" In every version, the question to answer is the same one — which expenses are yours, and what happens when they rise?

What is percentage rent?

Percentage rent is additional rent calculated as a share of the tenant’s sales above an agreed threshold, on top of base rent. It is common in retail and food service, where a landlord wants exposure to how the location actually performs.

The Fork CPAs give a worked example: a lease "calls for a base rent of $5,000 per month plus 9% of sales over $80,000 each month." At $100,000 of monthly sales that adds $1,800, and with $300 of property taxes and $700 of CAM and insurance the occupancy cost reaches $7,800 a month, or 7.8% of sales. Three numbers decide whether a percentage rent clause helps or hurts: the base rent, the percentage rate, and the sales threshold where it starts.

The definition of "sales" is negotiable and worth negotiating. The Fork CPAs note that "percentage rent is typically calculated based on net sales — so including comps and discounts — rather than gross sales," that mandatory service charges should not count, and that off-premise sales such as third-party delivery and catering may be worth excluding. Done well, the clause shifts some risk to the landlord in a bad year; done carelessly, it charges you rent on revenue you never really kept.

What is the difference between rentable and usable square feet?

Usable square footage is the space you actually occupy; rentable square footage is that space plus a share of the building’s common areas, and rent is charged on the rentable number. The federal government’s own leasing manual, the GSA Public Buildings Service Pricing Desk Guide, defines rentable square footage as "the area for which the customer agency is charged Rent; may include a share of building support and common areas" and usable square footage as "the area where a customer agency normally houses personnel or furniture."

The bridge between them is what brokers call the load factor and the GSA calls the common area factor: "a conversion factor determined by the building owner and applied to the usable square footage to determine the rentable square footage for the space." GSA’s standard lease template spells out the arithmetic with a concrete case: "11,500 RSF and 10,000 ABOA SF will have a CAF of 15%."

The consequence is direct. In that example you pay for 11,500 square feet and can put furniture in 10,000, so a rent quoted per rentable square foot understates your true cost per square foot of working space by the same 15%. When comparing two spaces, compare the rent against the square footage you can actually use.

What is an escalation clause?

An escalation clause is the provision that increases what you pay over the life of the lease, usually annually, either by a fixed percentage or in step with an inflation index or the landlord’s actual costs.

The GSA’s standard commercial lease template shows the mechanism in real lease language. Its Operating Costs Adjustment paragraph reads: "Beginning with the second year of the Lease and each year thereafter, the Government shall pay annual incremental adjusted rent for changes in costs for cleaning services, supplies, materials, maintenance, trash removal, landscaping, water, sewer charges, heating, electricity, and certain administrative expenses attributable to occupancy," with the adjustment "determined by multiplying the base rate by the annual percent of change in the Cost-of-Living Index." The lease sets a base rate per rentable square foot, and everything after year one moves off that base.

For a tenant, the thing to model is not year one but year five. An escalation compounding on top of a rent already near the top of your occupancy-cost range is how an affordable lease becomes an unaffordable one without anybody renegotiating anything. Ask whether increases are capped, and run the last year of the term as well as the first.

What is a tenant improvement allowance?

A tenant improvement allowance is money the landlord contributes toward building the space out for your use. The GSA Pricing Desk Guide defines it as "the funding source that enables the space to be built out for occupancy to meet a customer agency’s specific requirements," and defines the improvements themselves as "the finishes and fixtures that typically take space from the shell condition to a finished, usable condition."

Two things about it are easy to miss. It is usually stated as a dollar amount per square foot, so it scales with the space rather than with what your build-out actually costs — and a food-service or medical fit-out routinely costs far more per square foot than a retail one. And an allowance is rarely free money: it is commonly amortised into the rent over the term, which means a generous allowance and a higher base rent are frequently the same deal described two ways.

What is a personal guaranty on a commercial lease?

A personal guaranty is a separate promise, signed by an individual, to pay the lease obligations if the business does not. Cornell’s Legal Information Institute defines a guaranty as "an undertaking or a promise from a guarantor" that amounts to "an assurance of the future payment of another person’s debt," and a guarantor as a party who "assumes the financial obligation of another party in the event that the original party is unable to fulfill their obligation."

It is the clause that puts your personal assets behind the lease, and standard forms are written to be hard to escape. The widely used AIR Commercial Real Estate Association Guaranty of Lease form, published on the California Attorney General’s site, has guarantors "jointly, severally, unconditionally and irrevocably guarantee the prompt payment by Lessee of all rents and all other sums payable by Lessee under said Lease." Under the same form the landlord "shall have the right to proceed against Guarantors hereunder following any breach or default by Lessee without first proceeding against Lessee and without previous notice to or demand upon either Lessee or Guarantors."

Forming an LLC does not undo this. If you sign a guaranty, the limited-liability structure protects you from the business’s other obligations but not from the one you personally guaranteed. What is negotiable is scope: a cap on the amount, a limit to the first year or two of the term, or a burn-off once the business has paid on time for a defined period.

What is a certificate of occupancy?

A certificate of occupancy is the municipal document stating what a building may legally be used for and confirming it may be occupied at all. The requirements are local, but New York City’s Department of Buildings states the general shape plainly: a certificate of occupancy "states a legal use and/or type of permitted occupancy of a building," and "no one may legally occupy a building until the Department has issued a CO or Temporary Certificate of Occupancy."

The trap for a new tenant is the change-of-use case. In New York City’s wording, "existing buildings must have a current or amended CO when there is a change in use, egress or type of occupancy" — so a space that legally held a retail shop may need an amended certificate before it can hold a restaurant, and obtaining one can take months and construction work. Confirm the certificate covers your intended use, in writing, before the lease commences rather than after.

What do assignment and subletting mean in a lease?

Assignment transfers the whole remaining lease to someone else; subletting hands part of it over while you stay on the hook. Cornell’s Legal Information Institute draws the line precisely: "if assigning, A would be giving the entire balance of the term to C, with no reversion to anyone; whereas if subleasing, A would be giving the balance to C for a limited period of the remaining term."

Neither necessarily releases you. On the sublease side Cornell is explicit: "there is no privity of contract under the sublease between the owner of the property and the sublessee. The original lessee still has the responsibility to fulfill the lease obligations." A landlord can also forbid the arrangement outright — "the property owner could forbid a tenant to sublease the estate."

These clauses are the exit route from a five- or ten-year commitment, which makes them worth reading before signing rather than during a crisis. The terms that matter are whether the landlord’s consent may be withheld unreasonably, whether selling the business counts as an assignment, and whether you are released on transfer or remain liable for the rest of the term.

How do I know whether a specific location can support these costs?

Every term above changes what a lease costs. None of them tells you what the address will earn — and that is the side of the equation the lease document is silent about. A triple net quote at $42 per square foot is a good deal or a fatal one depending entirely on the foot traffic, the residential density within a short walk, how many comparable businesses already serve those people, and how easily a customer can stop and park.

That is what an OpenReady LocIQ report calculates for one specific commercial address before you sign: the revenue the location’s real-world conditions can plausibly support, the occupancy-cost range that implies for the rent you have been quoted, and whether the two actually line up. One report, one price, results in minutes — worth running before a lease you will be holding for five years.