Net Operating Income (NOI) is calculated by subtracting a property's total operating expenses from its gross operating income. Mortgage payments, capital expenditures, and income taxes are excluded. NOI is used to measure a property's profitability before financing, making it the foundation for cap rate calculations and property valuations.
NOI = Gross Operating Income - Operating Expenses
If you own or are evaluating a rental property, NOI is the most important number you need to know. It tells you how much income the property generates from its day-to-day operations, independent of how it is financed or what tax situation you are in. Every major real estate metric, including cap rate, debt service coverage ratio, and property valuation, runs through NOI.
This guide walks through the exact formula, a full step-by-step calculation with real numbers, what to include and exclude, the most common calculation mistakes, and how NOI connects to the other numbers that matter. oss Potential Income (GPI)
The complete formula has three stages:
This is the maximum possible income the property could generate if it were fully occupied at market rent every day of the year, plus any other income sources.
GPI = Total Scheduled Rent + Other Income
Other income includes parking fees, laundry facilities, storage unit rentals, pet fees, vending machines, and any other revenue the property generates beyond rent.
Gross operating income adjusts for the reality that properties are not always fully occupied and not every tenant always pays.
GOI = GPI - Vacancy and Credit Loss
Vacancy and credit loss accounts for both vacant units between tenants and the risk of non-payment. Industry standard for stabilized residential properties is 5% of GPI, though this varies by market and property condition.
NOI = GOI - Operating Expenses
Operating expenses are all recurring costs required to run the property. The next section covers exactly what to include.
Getting NOI right depends entirely on using the correct expense inputs. These are the operating expenses that belong in the calculation:
Property taxes. Real estate taxes levied by local government. These vary significantly by state, county, and municipality. Always use the actual tax bill, not an estimate.
Insurance. Landlord or building insurance covering the structure and liability. Tenant contents insurance is the tenant's responsibility and is not included.
Property management fees. If the property is professionally managed, the management fee (typically 8% to 12% of gross rent) is an operating expense. If you self-manage, it is reasonable to include a management fee equivalent anyway to reflect the true cost of your time, or to make the NOI comparable to professionally managed alternatives.
Maintenance and repairs. Routine upkeep, minor repairs, landscaping, snow removal, pool maintenance, HVAC servicing, and general property care. A common rule of thumb is to budget 1% of property value per year for maintenance, though older properties often run higher.
Utilities. Only utilities the landlord pays directly. If tenants pay their own utilities, exclude them. Common landlord-paid utilities include water, trash, and common area electricity in multifamily buildings.
Administrative costs. Accounting, legal fees, software, office supplies, and similar administrative expenses directly related to operating the property.
Advertising and leasing costs. Marketing expenses to attract new tenants and leasing fees paid when a new tenant is placed.
HOA or condo fees. If the property is in an HOA or condo association, those fees are an operating expense.
These costs are often incorrectly included in NOI calculations:
Mortgage payments (debt service). Principal and interest payments on the loan are excluded. NOI is designed to measure the property's performance independent of financing. Two investors buying the same property with different loan amounts would arrive at different results if debt service were included, making comparison impossible. Debt service is deducted after NOI to calculate cash flow.
Capital expenditures (CapEx). Major, infrequent improvements like replacing a roof, HVAC system, or kitchen are excluded from NOI. These are one-off investments, not recurring operating costs. Most investors track CapEx separately and account for it in after-tax cash flow analysis.
Income taxes. Personal or corporate income taxes depend on the investor's specific tax situation and are not a property-level operating cost.
Depreciation and amortization. These are accounting concepts, not cash expenses. They do not appear in NOI.
A 6-unit apartment building in Atlanta. Each unit rents for $1,400 per month.
| Income Source | Annual Amount |
|---|---|
| Gross rent (6 units × $1,400 × 12) | $100,800 |
| Parking fees (6 spaces × $50 × 12) | $3,600 |
| Laundry income | $1,200 |
| Gross Potential Income | $105,600 |
Using a 6% vacancy allowance for an Atlanta mid-tier multifamily property:
$105,600 × 6% = $6,336 vacancy and credit loss
GOI = $105,600 - $6,336 = $99,264
| Expense | Annual Amount |
|---|---|
| Property taxes | $9,600 |
| Insurance | $3,200 |
| Property management (10%) | $9,926 |
| Maintenance and repairs | $6,000 |
| Water and trash (landlord-paid) | $4,800 |
| Landscaping | $1,800 |
| Administrative and legal | $1,200 |
| Total Operating Expenses | $36,526 |
NOI = $99,264 - $36,526 = $62,738
This property generates $62,738 per year in net operating income.
NOI is the input for two of the most commonly used real estate investment calculations.
Cap rate:
Cap Rate = NOI / Property Value × 100
If the Atlanta property above is worth $900,000:
Cap Rate = $62,738 / $900,000 × 100 = 6.97%
Estimating property value from NOI:
If comparable properties in the Atlanta submarket trade at a 7% cap rate, you can use the NOI to estimate what this property could be worth:
Property Value = NOI / Cap Rate
Property Value = $62,738 / 0.07 = $896,257
This is the income approach to property valuation. It is how commercial appraisers and institutional investors price income-producing real estate, and it shows directly why improving NOI increases property value. A $5,000 improvement in annual NOI on a property trading at a 7% cap rate increases its implied value by approximately $71,000.
NOI and cash flow are related but distinct, and confusing them is one of the most common mistakes in property analysis.
NOI measures the property's performance before financing. It answers the question: how profitable is this asset on its own, regardless of how it is owned?
Cash flow is what you actually put in your pocket after the mortgage is paid. It answers the question: after all costs including debt service, how much money does this investment generate for me?
Cash Flow = NOI - Debt Service
Using the Atlanta example with a $675,000 mortgage at 7% interest over 30 years:
Annual debt service: approximately $53,940
Cash Flow = $62,738 - $53,940 = $8,798
The NOI is $62,738. The cash flow after debt service is $8,798. The difference is the cost of the mortgage. NOI shows you how the asset is performing. Cash flow shows you how the investment is performing for you specifically.
This distinction matters because two investors can buy the same property at the same price and arrive at identical NOIs but completely different cash flows, depending on how much they borrowed and at what rate.
Lenders can use NOI to calculate the Debt Service Coverage Ratio, which measures whether the property generates enough income to cover its loan payments.
DSCR = NOI / Annual Debt Service
Using the Atlanta example:
DSCR = $62,738 / $53,940 = 1.16
Most lenders require a DSCR of at least 1.20 to 1.25 for a standard investment property loan. A DSCR below 1.0 means the property does not generate enough income to cover its mortgage, which disqualifies it for most conventional lending. Understanding your NOI relative to your expected loan payments before making an offer helps you assess whether the deal will be financeable.
Using asking rent rather than market rent. If a property has below-market rents, using the actual collected rent understates the property's income potential. If it has above-market rents, using that figure overstates it. Market rent analysis gives a more accurate picture of stabilized NOI.
Ignoring vacancy. Assuming 100% occupancy inflates GOI and therefore overstates NOI. Even in tight rental markets, vacancy between tenants, evictions, and credit losses occur. Always apply a vacancy factor.
Underestimating maintenance. New investors frequently budget $1,000 to $2,000 per year for maintenance on a property that realistically requires $6,000 to $10,000. Older properties, properties with deferred maintenance, and properties in high-cost-of-labor markets all require more generous maintenance reserves.
Including capital expenditures in operating expenses. Replacing a roof is not an operating expense. It is a capital expenditure. Including it in NOI understates the property's profitability in years when major CapEx occurs, while overstating it in years when no CapEx is needed. Track CapEx separately and model it in your cash flow analysis.
Using the seller's pro forma NOI without verification. Sellers often present optimistic pro forma NOI figures based on market rents and minimal expense assumptions. Always reconstruct NOI from actual rent rolls, trailing 12-month expense statements, and your own market-rate vacancy and management cost assumptions.
Forgetting property management fees when self-managing. If you plan to manage the property yourself, it is still good practice to include a management fee in your NOI calculation. It gives you an accurate comparison against professionally managed alternatives and accounts for the real opportunity cost of your time. It also protects your analysis if you ever need to transition to professional management.
NOI is a powerful starting point, but it is not a complete investment analysis on its own. Here is how it connects to the full picture.
Cap rate tells you how the market is pricing the property's NOI relative to similar assets. Cash flow tells you what the investment actually produces for you after financing. DSCR tells you whether the property will qualify for the loan you need. And multi-year NOI projections, accounting for rent growth, expense inflation, and vacancy trends, show you how the property performs over time, not just at the point of purchase.
Calm Sea's investment property tracker models all of this in one place. You enter your property's income, expenses, and loan details, and Calm Sea calculates your NOI, cap rate, cashflow, and equity position. It then projects all of them forward year by year and rolls the property into your total net worth view alongside your other assets, so you can see how your investment property fits into your complete financial picture.
Calm Sea is a personal finance planning tool. Nothing in this article constitutes financial advice. All projections and calculations are illustrative estimates. Always conduct your own due diligence and consult a qualified financial adviser or real estate professional before making investment decisions.
Cap rate (capitalization rate) is the ratio of a property's net operating income to its value, expressed as a percentage. Learn the formula, worked examples, what counts as a good cap rate, and how it fits into a complete investment property analysis.
June 21, 2026
Looking for a financial independence tracking app to monitor your path to FIRE? Learn what features matter most, which metrics to track, and how the right tool can help you retire early.
June 11, 2026
