BRIEFCASE GUIDES / COMMERCIAL REAL ESTATE
Net operating income (NOI) is the money a property earns from operations after paying its operating expenses, but before mortgage payments, income taxes, depreciation, and capital spending. It is the single number that cap rates, DSCR, debt yield, and most valuations are built on.
EDUCATIONAL NOTE
This page is general information for learning purposes, not lending, tax, legal, or investment advice. Briefcase is a media and marketing company, not a lender, broker, or investment adviser. Terms, ratios, and eligibility vary by lender, sponsor, and deal, so confirm every figure with a licensed professional before you act.
If you remember one thing, make it this: NOI describes the building, not the owner. Two investors who buy the same apartment complex with different loans will have different cash flow, but the property has one NOI. That is why lenders, appraisers, and buyers all start from it.
This guide walks through the formula line by line, shows a full worked example with round hypothetical numbers, lists the expenses people wrongly include or leave out, and explains how NOI connects to the other ratios on this site.
01
FORMULA
NOI = Effective gross income − Operating expenses
Effective gross income (EGI) starts with gross potential rent, the rent you would collect if every unit or suite were leased at market rates all year. You subtract vacancy and credit loss, then add other income such as parking, laundry, storage, pet fees, utility reimbursements, and in commercial leases, expense recoveries paid by tenants.
Operating expenses are the recurring costs of running the property: property taxes, insurance, utilities the owner pays, repairs and maintenance, property management fees, payroll for on-site staff, landscaping, snow removal, trash, administrative costs, and marketing. Many underwriters also deduct a replacement reserve, which we cover below.
02
The most common NOI error is subtracting things that belong below the line. These items matter to your returns, but they are financing, tax, or capital decisions, so they stay out of NOI:
01
Mortgage principal and interest (debt service). This is what DSCR compares NOI against, so it cannot also be inside NOI.
02
Depreciation and amortization. These are non-cash accounting deductions. The IRS treats them as tax items, not operating cash costs.
03
Income taxes of the owner or the entity.
04
Capital expenditures such as a new roof, parking lot replacement, or a unit renovation program. Many lenders handle these with a reserve line instead.
05
Leasing commissions and tenant improvement allowances in commercial deals, which are usually tracked separately as leasing costs.
06
Owner draws, partnership distributions, and asset management fees paid to a sponsor.
A quick test: if the expense would disappear when you paid off the loan or changed owners, it probably does not belong in NOI.
03
The numbers below are a hypothetical example in round figures, chosen to make the math easy to follow. They are not market data.
Gross potential rent (24 units x $1,500 x 12)
$432,000
Less vacancy and credit loss at 7%
−$30,240
Plus other income (parking, laundry, fees)
$14,400
Effective gross income
$416,160
Property taxes
−$52,000
Insurance
−$26,000
Utilities paid by owner
−$31,000
Repairs and maintenance
−$28,000
Management fee at 5% of EGI
−$20,808
Payroll, admin, marketing
−$24,000
Replacement reserve ($300 per unit)
−$7,200
Total operating expenses
−$189,008
Net operating income
$227,152
That works out to an expense ratio of about 45% of EGI. Expense ratios vary widely by asset type, age, location, and who pays utilities, so compare against the actual operating statements of similar properties rather than a rule of thumb.
04
FORMULA
Value = NOI ÷ Cap rate
Commercial property is mostly priced on income. If buyers in a market are paying a 6.0% cap rate for similar buildings, the example property above implies a value of about $3.79 million ($227,152 ÷ 0.06). At a 6.5% cap rate the same NOI implies about $3.49 million.
This is why NOI is so heavily scrutinized in a sale. Every extra dollar of sustainable NOI is worth roughly 15 to 17 dollars of value at those cap rates. It is also why sellers are tempted to show NOI with low vacancy, deferred maintenance, or no management fee. Read our guide to what a cap rate is and what counts as a good one before you lean on any single number.
05
Lenders size loans from NOI in two common ways. The debt service coverage ratio divides NOI by annual debt service, so a property with $227,152 of NOI and $175,000 of annual payments has a DSCR of about 1.30. Debt yield divides NOI by the loan amount, so the same NOI on a $2.5 million loan is a 9.1% debt yield.
Because both tests start from NOI, lenders build their own underwritten NOI. They typically use in-place rents rather than pro forma rents, apply their own vacancy factor, add a management fee even if the owner self-manages, and insert reserves. Their NOI is often lower than the broker package shows, and that gap is the most common reason loan proceeds come in below expectations.
06
You will see NOI quoted three ways, and mixing them up causes bad decisions:
01
Trailing 12 (T12) NOI uses the actual income and expenses from the last twelve months. It is the most reliable, because it already happened.
02
In-place or annualized NOI takes the current rent roll and annualizes it, sometimes paired with trailing expenses. It captures recent lease-up or rent increases that the T12 has not fully absorbed.
03
Pro forma NOI is a projection. It assumes future rents, occupancy, and expense savings. It is useful for planning a value-add strategy and dangerous when used to price a deal as if it were already true.
When a marketing package shows a strong pro forma NOI, ask for the T12 and the current rent roll, and rebuild NOI yourself.
07
01
Using last year's property tax bill on a property that will be reassessed at the sale price.
02
Leaving out a management fee because the seller self-manages. A buyer or lender will add one back.
03
Ignoring insurance renewals. Premiums can move sharply at renewal, so get a current quote rather than relying on the seller's old policy.
04
Counting one-time income, like a lease termination fee, as if it will recur.
05
Treating capital repairs as operating expenses in one year and leaving them out the next, which makes NOI look volatile or inflated.
06
Comparing NOI across properties where tenants pay different expenses. A NNN retail building and a gross-lease office building can have similar rents and very different NOI.
08
There are only two levers: raise effective income or lower operating expenses. On the income side, owners reduce vacancy with better leasing and renewals, bring below-market rents to market at turnover, add fee income such as storage or parking, and recover more expenses in commercial leases. On the expense side, they appeal property tax assessments, rebid insurance and service contracts, cut utility waste with submetering or efficient fixtures, and use software to reduce staff hours per unit.
Marketing sits on the income side of that equation. Faster lease-up, better renewal communication, and resident retention all show up in vacancy and credit loss, which is often the biggest controllable line in the NOI statement. That is the work Briefcase Studio does for multifamily and property management teams.
TAKEAWAYS
01
NOI = effective gross income minus operating expenses.
02
Debt service, depreciation, income taxes, and capital projects stay out of NOI.
03
Value is roughly NOI divided by the market cap rate, so small NOI changes move value a lot.
04
Lenders rebuild NOI conservatively before sizing DSCR and debt yield tests.
05
Always ask whether a quoted NOI is trailing, in-place, or pro forma.
SOURCES
Every figure on this page links to the primary or named source we checked on November 9, 2026. Worked examples use round hypothetical numbers and are labeled as such.
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