What is NOI in real estate?
NOI in real estate is a property’s yearly income from rents and other sources, minus vacancy and the costs of running the building, before mortgage payments, capital projects, depreciation and income taxes. A 12-unit building that collects $177,000 and spends $69,000 to operate has $108,000 of NOI.
NOI ignores how the building is financed and who owns it, which is what makes it useful. Two buyers with very different loans can look at the same building and agree on its NOI. Cap rate, value, debt service coverage and cash-on-cash return all start from this one number, so an error in NOI carries through to every other figure in the deal.
What does NOI stand for?
NOI stands for net operating income. “Net” means after expenses, “operating” means from running the property (not from financing or selling it), and “income” means the figure is measured over a year unless stated otherwise.
You’ll see the abbreviation in offering memos, appraisals, loan applications and T-12 statements. Lenders sometimes report a related figure, net cash flow (NCF), which subtracts replacement reserves and other capital items from NOI. When two documents disagree, check which one is being used.
NOI meaning in real estate, in plain terms
In plain terms, NOI is what the building would hand an owner each year if the owner had no mortgage and paid no income tax. It is the building’s earning power, separated from the owner’s choices.
That separation is why buyers pay for NOI, not for cash flow. A seller with a large loan may show thin cash flow on a building with strong NOI. A seller with no loan may show cash flow equal to NOI. The building, and its value, is the same either way.
The definition of NOI in real estate is the same for a duplex, a 200-unit complex or an office building. What changes is the list of expenses. Apartment owners usually carry more of the operating costs themselves, such as common-area utilities, turnover and on-site staff, while many commercial leases pass those costs to tenants.
What is an NOI used for?
An NOI figure is used to value a property, size its loan and compare it with other buildings. Almost every number in an apartment sale is built on it.
- Value: NOI divided by the market cap rate. $108,000 of NOI at a 7% cap rate supports about $1,543,000.
- Cap rate: NOI divided by price, the standard way to quote and compare apartment pricing.
- Loan size: lenders divide NOI by the yearly loan payment (the debt service coverage ratio) and cap the loan where that ratio hits their minimum, often 1.25x.
- Cash flow: NOI minus debt service is the pre-tax cash an owner takes home.
- Performance: tracking NOI year over year shows whether management is raising income faster than costs.
The NOI formula
NOI equals effective gross income minus operating expenses. Effective gross income is gross potential rent, minus vacancy and credit loss, plus other income from the property.
Operating expenses are the recurring costs of running the building. Three items are deliberately left out: debt service (mortgage principal and interest), capital expenditures such as a new roof or boiler, and depreciation. Debt service reflects financing. Capital expenditures are periodic investments rather than yearly running costs. Depreciation is a tax deduction, not a cash outlay; the IRS has owners recover the cost of residential rental buildings over 27.5 years (IRS Publication 527), and none of that belongs in NOI.
- Gross potential rent: every unit at its lease or market rent for twelve months.
- Minus vacancy and credit loss: empty units, concessions and unpaid rent.
- Plus other income: laundry, parking, pet fees, storage, utility reimbursements.
- Equals effective gross income (EGI).
- Minus operating expenses: property taxes, insurance, owner-paid utilities, repairs and maintenance, management, payroll, landscaping and snow removal, trash, pest control, legal and accounting, advertising.
- Equals net operating income. Exclude mortgage payments, capital improvements, depreciation, income taxes and owner personal expenses.
Which expenses are included in NOI?
NOI includes the recurring costs of running the building and excludes financing, capital projects, depreciation and the owner’s personal costs. The line between a repair and a capital improvement causes the most arguments, so the table sorts the usual items.
The IRS draws a similar line for tax purposes: repair and maintenance costs can generally be deducted, while an expense that results in a betterment, restores the property or adapts it to a new use must be capitalized and depreciated (IRS Publication 527). NOI follows the same logic even though it isn’t a tax figure.
| Item | In NOI? | Why |
|---|---|---|
| Property taxes | Yes | Recurring cost of owning and operating |
| Insurance | Yes | Recurring; use the current quote |
| Owner-paid utilities | Yes | Recurring operating cost |
| Routine repairs (a leaky faucet, a broken window) | Yes | Keeps the building running as it is |
| Management fee | Yes | Charge it even if you self-manage |
| Mortgage principal and interest | No | Financing, not operations |
| New roof, boiler or full unit renovation | No | Capital improvement |
| Depreciation | No | Tax deduction, not a cash cost |
| Owner’s income tax, car, phone | No | Personal, not the property’s |
How to use the NOI calculator
Enter four figures: gross annual rent at full occupancy, other annual income, a vacancy and credit-loss percentage, and annual operating expenses without debt service or capital projects. The calculator returns the vacancy and credit-loss amount, effective gross income, operating expenses, NOI and the expense ratio.
With the default inputs ($360,000 of gross rent, $9,000 of other income, 6% vacancy and $150,000 of expenses), vacancy removes $21,600, effective gross income is $347,400 and NOI is $197,400, at a 43% expense ratio. Copy the NOI into the cap rate calculator to see value, or into the DSCR calculator to see the loan it supports.
A worked example
A 12-unit building has gross potential rent of $180,000 a year, an average of $1,250 per unit per month. A 5% vacancy allowance removes $9,000, and laundry and parking bring in $6,000, for effective gross income of $177,000.
Operating expenses: property taxes $24,000, insurance $9,000, owner-paid utilities $12,000, repairs and maintenance $10,000 and management $14,000, a total of $69,000. NOI is $177,000 minus $69,000 = $108,000. At a 7% cap rate, that income supports a value of about $1,543,000.
How NOI and cap rate work together
NOI and cap rate work together through one formula: value equals NOI divided by the cap rate. NOI is what the building earns. The cap rate is the yearly return buyers in that market accept on that kind of income. Put the two together and you get a price.
Using the 12-unit building above, $108,000 of NOI at a 7% cap rate is $108,000 ÷ 0.07 = about $1,543,000. If buyers in the area are paying 6.5% instead, the same NOI supports about $1,662,000. At 7.5%, it supports $1,440,000. The NOI never moved. The rate did, and it changed the price by more than $100,000 in each direction.
The formula also runs the other way. Divide NOI by a price and you get the cap rate that price implies: $108,000 ÷ $1,650,000 is about 6.5%. Multiply a price by a cap rate and you get the NOI a buyer needs to justify it. A buyer who will pay a 7% cap rate needs $105,000 of NOI to pay $1,500,000, and $115,500 to pay $1,650,000.
Because the two numbers multiply each other, small errors in NOI become large errors in value. Leaving out a $5,000 insurance increase looks minor on a T-12, but at a 7% cap rate it overstates value by about $71,000. Get the NOI right before you argue about the cap rate.
| Cap rate | Value of $108,000 NOI | Change from 7% |
|---|---|---|
| 6.0% | $1,800,000 | +$257,000 |
| 6.5% | $1,662,000 | +$119,000 |
| 7.0% | $1,543,000 | Base |
| 7.5% | $1,440,000 | -$103,000 |
| 8.0% | $1,350,000 | -$193,000 |
A second example: a 6-unit building with owner-paid utilities
Small buildings where the owner pays utilities often have expense ratios near or above half of income, and NOI shows why that matters. Take a 6-unit building with rents of $1,100 a month per unit.
Gross potential rent is $79,200. A 5% vacancy allowance removes $3,960, and coin laundry adds $1,800, for effective gross income of $77,040. Expenses total $37,693, so NOI is $39,347 and the expense ratio is about 49%. At a 7.5% cap rate, that NOI supports about $524,600.
Now suppose the owner starts billing tenants back for water, sewer and trash where local rules allow, and recovers $7,200 a year. NOI rises to $46,547 and value at the same 7.5% cap rate rises to about $620,600, an increase of roughly $96,000 from one change. Check your state and city rules before you add a utility charge to existing leases, since many require notice or limit when terms can change.
| Line | Amount |
|---|---|
| Gross potential rent (6 × $1,100 × 12) | $79,200 |
| Vacancy (5%) | -$3,960 |
| Laundry income | $1,800 |
| Effective gross income | $77,040 |
| Property taxes | -$9,800 |
| Insurance | -$4,200 |
| Owner-paid utilities | -$10,800 |
| Repairs and maintenance | -$6,000 |
| Management (7% of EGI) | -$5,393 |
| Trash | -$1,500 |
| NOI | $39,347 |
Pro forma NOI vs actual NOI
Pro forma NOI is a projected NOI based on what a property is expected to earn after changes such as rent increases, renovations or new management, while actual NOI is what it earned over the trailing twelve months. Brokers often price buildings on pro forma figures. Buyers and lenders mostly pay for actual ones.
Using the same 12-unit building: suppose renovated units nearby rent for $1,400 a month. Pro forma gross rent becomes $201,600. After 5% vacancy ($10,080) and the same $6,000 of other income, EGI is $197,520. Expenses rise to $72,000 for higher management and insurance, so pro forma NOI is $125,520, about $17,500 more than actual.
At a 7% cap rate, that gap is worth about $250,000 of price ($1,793,000 on pro forma vs $1,543,000 on actual). A seller who wants to be paid for the pro forma usually needs signed leases at the higher rents. A buyer who pays for it is paying in advance for work the buyer will do and risk the buyer will carry.
| Line | Actual (T-12) | Pro forma | Difference |
|---|---|---|---|
| Gross potential rent | $180,000 | $201,600 | +$21,600 |
| Vacancy (5%) | -$9,000 | -$10,080 | -$1,080 |
| Other income | $6,000 | $6,000 | $0 |
| Effective gross income | $177,000 | $197,520 | +$20,520 |
| Operating expenses | -$69,000 | -$72,000 | -$3,000 |
| NOI | $108,000 | $125,520 | +$17,520 |
| Value at 7% cap rate | $1,543,000 | $1,793,000 | +$250,000 |
How to check a pro forma
Test a pro forma line by line against evidence. A few questions catch most problems.
- Are the projected rents backed by signed leases at comparable buildings, or by asking rents?
- Does the vacancy figure allow for units sitting empty during renovation?
- Are property taxes based on the new purchase price? In states that reassess on sale, such as California under Proposition 13, the buyer’s tax bill can be several times the seller’s.
- Does the expense line include market-rate management and a current insurance quote?
- Is the renovation budget in the purchase math, even though it sits outside NOI?
Choosing a vacancy rate and expense figures
Use the building’s own history for vacancy, then check it against the local market and against what lenders will assume. A fully leased building still loses income to turnover, concessions and unpaid rent. For comparison, HUD underwrites Section 223(f) loans on market-rate apartments with a 7% vacancy factor and 5% for affordable properties with a rent advantage, under Mortgagee Letter 2025-03.
For expenses, use actual bills rather than estimates where you can. Pull the last property tax bill, the insurance declarations page and twelve months of utility statements. Budget management at a market rate even if you do it yourself, because the next owner will have to pay someone. Treat repair invoices with care: replacing a faucet is a repair, while replacing every water heater in the building is a capital project that stays out of NOI.
Watch the trend, not only the total. Insurance premiums and property taxes can rise faster than rents, and an expense line that looks fine on last year’s T-12 can be thousands of dollars short once the renewal quote arrives.
How to read the result
Divide operating expenses by effective gross income to get the expense ratio; in the worked example it is about 39%. A ratio far below your local norm often means an expense is missing. One far above it may point to utilities the owner pays, deferred maintenance being booked as repairs, or management that is not working.
When evaluating a purchase, calculate NOI twice: once from the seller’s trailing twelve months, and once from your own budget with market-rate management, current insurance quotes and property taxes reassessed at your purchase price. The gap between the two is where most underwriting surprises live.
Common mistakes
These errors show up regularly in offering memos and owner statements.
- Subtracting mortgage payments, which understates NOI and double-counts financing later.
- Counting a one-time capital project as an operating expense, or the reverse.
- Leaving out management because the owner self-manages.
- Using scheduled rent with no allowance for vacancy or unpaid rent.
- Mixing time periods, such as annual rent with a single month of expenses.
Raising NOI before you sell
Because buyers price apartment buildings on NOI, every dollar of lasting NOI you add before a sale is worth many dollars of price. At a 6.5% cap rate, $10,000 of added yearly NOI supports about $154,000 of value. The fastest gains usually come from billing back utilities, bringing below-market leases up at renewal, and appealing an inflated tax assessment.
Not every owner wants to spend another year on that work. Skyline Capital buys 5+ unit buildings nationwide as they stand. We buy directly, close on your timeline, and can work inside 1031 deadlines.
