How to Calculate Triple Net Rent: NNN Lease Charges, Formula, and Examples

Total annual rent under a triple net lease = (base rent PSF + NNN charges PSF) x rentable square feet, where NNN charges PSF = (property taxes + building insurance + common area maintenance) divided by the building's rentable square feet, then multiplied by the tenant's pro rata share. Monthly rent is that annual figure divided by 12. So a 5,000 square foot suite at $24.00 base plus $8.00 in NNN charges pays $160,000 a year, or about $13,333.33 a month.

Triple net rent trips people up because the base rent is only part of what you actually pay. The rest is the operating cost pass-through, quoted per square foot, and it moves every year. This guide gives you the formula, a worked example, a worksheet, and the terms that change the total.

Last updated July 2026.

How do you calculate triple net rent?

Add the base rent per square foot to the NNN charges per square foot, then multiply by the rentable square footage of the space. NNN charges per square foot come from the building's recoverable operating costs (taxes, insurance, and common area maintenance) divided by the building's rentable area, allocated by your pro rata share. Divide the annual total by 12 for the monthly payment.

In practice you carry two rates. Base rent is set in the lease and steps up on a schedule; the NNN rate is estimated at the start of each year and trued up later. Both are quoted PSF so you can compare deals across buildings of different sizes. Pulling those rates out of a signed document is exactly what our NNN lease abstraction workflow captures, field by field, with a citation back to the lease page.

What is included in NNN charges?

NNN charges include the three "nets": property taxes, building insurance, and common area maintenance (CAM). Property taxes cover the real estate assessment. Insurance covers the landlord's property and liability coverage on the building. CAM covers the shared costs of running the property: landscaping, parking lot upkeep, snow removal, security, common area utilities, and routine repairs.

What counts as CAM is where leases differ most. A tight lease lists exclusions and caps; a loose one lets the landlord fold in items a tenant would rather not fund. That is the difference between a full triple net deal and the lighter NN and NNN structures. Read the definitions section, not just the label on the cover page.

How do you calculate the NNN per square foot?

Take the building's total recoverable operating costs for the year, divide by the building's rentable square footage, and you have the NNN rate PSF. That single rate applies to every tenant, and each funds its share through the pro rata mechanism. If a 50,000 square foot building has $400,000 in recoverable costs, the NNN rate is $8.00 PSF.

Note the phrase "recoverable." Not every dollar the landlord spends is billable. Capital improvements, leasing commissions, and certain management fees are often excluded, so the pool is smaller than the full operating budget. That pool is built from vendor bills, so landlords who automate the accounts payable behind those operating expenses reconcile faster and with fewer year-end disputes.

What is the difference between base rent and triple net rent?

Base rent is the fixed amount a tenant pays for the space itself, set in the lease and stepped up on a schedule. Triple net rent is base rent plus the tenant's share of taxes, insurance, and CAM. Base rent is predictable; the NNN portion is variable and reconciled to actual costs every year, which is why the total you pay can rise even when base rent holds flat.

A $24.00 gross quote and a $24.00 NNN quote are not the same deal. The gross number bundles operating costs into one figure; the NNN number sits on top of an $8.00 pass-through. Abstract both rates into a single view, which a standard lease abstract template is built to hold so nothing gets compared apples to oranges.

How do you calculate a tenant's pro rata share?

Divide the tenant's rentable square footage by the building's (or the applicable expense pool's) rentable square footage. A 5,000 square foot suite in a 50,000 square foot building has a 10% pro rata share, so that tenant funds 10% of the recoverable pool. The percentage is written into the lease and should be checked against the measured area.

Two wrinkles matter. The denominator can be the whole building or just a phase or parcel, and occupancy adjustments can shift the effective share in a partly vacant building. Getting the denominator wrong is one of the most common CAM reconciliation errors, and it compounds every month until someone catches it.

Are NNN charges estimated or actual?

Both. Landlords bill an estimate monthly based on the projected annual budget, then reconcile to actual costs after the year closes, usually within 90 to 120 days. If actual costs came in higher than estimated, the tenant owes a true-up; if lower, the tenant gets a credit or refund. You pay estimates in real time and settle the difference once.

This is why the number on your January invoice is provisional. Read the reconciliation and audit sections so you know when the statement arrives and how long you have to dispute it. The mechanics of that year-end settlement are covered in our guide to lease abstraction for property managers.

What is a triple net lease calculator?

A triple net lease calculator (or NNN lease calculator) is a simple tool that takes base rent PSF, the NNN rate PSF, and rentable square feet, then returns the annual and monthly rent. Some also back into the NNN rate from raw expense totals and a pro rata share. It is arithmetic you can do by hand, but a calculator keeps the inputs consistent.

The limit of any calculator is that it trusts the rates you feed it. A clean NNN PSF depends on the caps, exclusions, and pro rata definition inside the lease, which a spreadsheet does not read. That is the gap our lease abstraction software fills: it pulls the rates and the fine print together so the number you calculate matches the number you are owed.

Worked example (illustration only)

These are round, hypothetical numbers chosen to make the math clear. They are an example, not market data.

Assume a 5,000 RSF suite in a 50,000 RSF building at $24.00 base rent PSF. The building's annual recoverable costs are property taxes $200,000, insurance $50,000, and CAM $150,000.

Step 1, total the recoverable pool: $200,000 + $50,000 + $150,000 = $400,000.

Step 2, get the NNN rate PSF: $400,000 / 50,000 RSF = $8.00 PSF.

Step 3, get the pro rata share: 5,000 / 50,000 = 0.10, or 10%.

Step 4, combine the rates: $24.00 base + $8.00 NNN = $32.00 PSF all in.

Step 5, annual rent for the suite: $32.00 x 5,000 RSF = $160,000.

Step 6, monthly rent: $160,000 / 12 = $13,333.33.

Sanity check: 10% of the $400,000 pool is $40,000, which is exactly $8.00 x 5,000 RSF. The tenant's share of taxes ($20,000), insurance ($5,000), and CAM ($15,000) adds back to $40,000.

Monthly rent estimate worksheet

Every figure ties to the worked example above (5,000 RSF suite, 10% pro rata share).

Which lease terms change the triple net rent calculation?

The formula is simple; the lease language is where the real number lives. A handful of provisions can move the NNN rate more than the arithmetic suggests, so read these before you trust any estimate.

Expense caps. Many leases cap the annual growth of controllable expenses (typically CAM, not taxes or insurance). A well-drafted cap on controllable expenses keeps your CAM from spiking after a management change or a big repair year.

Gross-up provisions. In a partly vacant building, a gross-up provision restates variable costs as if the building were 95% to 100% occupied, which can raise a NNN tenant's bill. Check how the clause is written.

Base year vs true NNN. A modified gross or base year lease only passes through increases over a baseline year, while a true triple net passes through the full share from dollar one. Confusing the two skews the number badly.

Exclusions. Capital expenditures, leasing commissions, and landlord-side management fees are commonly excluded or capped. Every excluded dollar shrinks the recoverable pool and your PSF rate.

Reconciliation and audit rights. Estimates get trued up to actuals annually, and audit rights let you inspect the backup. For a fuller walkthrough of the underlying structure, see our explainer on the triple net lease.

Amendments that move pro rata share. Expansions, contractions, and remeasurements change the numerator or denominator, so an amendment can reset your share mid-term. If the abstract still shows the old percentage, every reconciliation after that is wrong.

Get the rates straight from the lease

A calculator is only as good as its inputs, and the inputs live in a signed document with caps, exclusions, and a pro rata definition a spreadsheet cannot see. Our NNN lease abstraction pulls the base rent schedule, NNN rate, pro rata share, caps, and audit rights out of each lease with a page citation for every field, so the triple net rent you calculate matches what you actually owe. Upload a lease and see the output before you commit.