Net Operating Income (NOI) in Commercial Real Estate

Published: March 24, 2026

Article by Ryan O'Connell, CFA, FRM

Net operating income is the single most important number in commercial real estate. Every major decision — property valuation, loan qualification, investment analysis — starts with NOI. Whether you are underwriting a 100-unit apartment complex or evaluating a triple-net retail center, understanding how NOI is calculated and what it includes (and excludes) is essential. This guide covers the NOI formula, its components, two worked examples across property types, and the limitations every CRE investor should understand.

What Is Net Operating Income (NOI)?

Net operating income (NOI) is a property’s total revenue minus all operating expenses, calculated before debt service, capital expenditures, and income taxes. It measures how effectively a property generates income from its operations — independent of how the purchase is financed.

In corporate finance, NOI is loosely analogous to operating income or EBITDA — both strip out financing and tax effects to focus on operational profitability, though the specific line items differ. For a deeper look at how operating income drives corporate valuation, see our guide to DuPont Analysis. NOI serves as the numerator in the cap rate calculation, the key input for DSCR analysis, and the foundation of multi-year DCF proformas.

Net Operating Income Formula: PGI, Vacancy, EGI, and Expenses

NOI is calculated using a waterfall that starts with potential gross income and works down through vacancy, other income, and operating expenses:

Where:

• PGI (Potential Gross Income) — the rent roll for in-place leases plus projected market rent for vacant or rollover space; represents income at full occupancy
• Vacancy & Collection Loss — income lost to unoccupied units and uncollected rent; typically 3–10%. For multifamily and short-term-lease assets, usually estimated as a percentage of PGI. For office and retail with longer leases, analysts often forecast vacancy lease-by-lease, projecting downtime between each expiration and the next lease-up.
• Other Income — non-rental revenue: parking, laundry/vending, storage, billboard or antenna leases
• Expense Reimbursements — amounts tenants reimburse for operating costs under NNN or expense-stop leases; flows into EGI as revenue
• EGI (Effective Gross Income) — actual collectible income from all sources
• Operating Expenses — recurring costs: property taxes, insurance, management fees, maintenance, utilities

What Is Included in Net Operating Income?

Income Sources

Commercial properties generate revenue from multiple sources beyond base rent. The mix depends on property type, lease structure, and physical amenities:

Operating Expense Categories

Operating expenses fall into two broad categories: fixed costs that remain relatively constant regardless of occupancy, and variable costs that fluctuate with the number of occupied units:

What NOI Excludes

Standard NOI explicitly excludes debt service (mortgage principal and interest), capital expenditures (roof replacement, HVAC systems, elevator modernization), income taxes (attributable to the investor, not the property), and depreciation (a non-cash charge — the NOI proforma is cash-flow-based). One important nuance: some appraisers and institutional underwriters deduct a recurring replacement reserve allowance above the NOI line when presenting stabilized or underwritten cash flow. Always confirm whether the NOI figure you are reviewing includes or excludes replacement reserves.

NOI Example: Multifamily Property Walkthrough

Consider a 100-unit apartment complex in Austin, Texas with an average monthly rent of $1,000 per unit. Multifamily properties use the percentage-of-PGI method for vacancy because leases are short-term and tenant turnover is relatively predictable:

Investors and appraisers apply a market cap rate to this NOI to estimate property value, and lenders use it to assess the DSCR.

NOI Example: NNN Retail Strip Center

Retail and office properties often use net leases, where tenants pay most operating expenses directly. This changes the NOI profile significantly compared to multifamily. Consider a 10,000 SF strip center with three tenants on NNN leases:

NOI vs Cash Flow: What NOI Does Not Include

NOI and cash flow are related but distinct concepts. NOI measures property-level operating performance, while the cash flow measures below it progressively subtract capital costs and financing:

NOI systematically overstates the actual cash an owner receives. Capital expenditures typically consume 10–20% of NOI over a property’s lifecycle, and can exceed 30% for institutional-quality portfolios tracked by NCREIF. A newly built Class A multifamily property might spend 5–10% of NOI on CapEx, while a 30-year-old office building could spend 20% or more. Ignoring CapEx when evaluating investment returns can lead to significant overestimates of actual performance. For a complete treatment of property-level cash flow projections, see our guide to CRE DCF proformas.

Where NOI Is Used

NOI is the building block for the three most important analytical frameworks in commercial real estate:

Cap Rate. The cap rate is the primary metric for quickly comparing income yield across CRE properties and markets. NOI is its core input. See our cap rate guide for interpretation by property type.

Debt Service Coverage Ratio (DSCR). Lenders use DSCR to test whether a property’s NOI is sufficient to cover its mortgage obligations. See our DSCR guide for how lenders use this metric in loan qualification.

DCF Proforma. In a multi-year DCF analysis, NOI is projected annually and then adjusted for capital expenditures and reversion to build the cash flow stream that is discounted to present value. See our CRE DCF proforma guide for the complete methodology.

How to Calculate NOI

Follow these five steps to calculate NOI for any commercial property:

1. Estimate Potential Gross Income (PGI) from the rent roll for in-place leases plus projected market rent for any vacant or rollover space.
2. Apply a vacancy and collection loss factor based on the property’s historical performance and local market conditions — use a percentage of PGI for short-term-lease assets, or forecast lease-by-lease downtime for longer-lease office and retail properties.
3. Add other income and expense reimbursements — parking, laundry/vending, storage, billboard leases, and any CAM or operating expense reimbursements from tenants — to arrive at Effective Gross Income (EGI).
4. Itemize all operating expenses, including property taxes, insurance, management fee (even if self-managed), utilities, maintenance, and administrative costs.
5. Subtract total operating expenses from EGI to arrive at Net Operating Income.

You can also evaluate your property’s cost efficiency using our Operating Expense Ratio Calculator, which compares operating expenses to effective gross income across different property types.

Common Mistakes When Calculating NOI

NOI is straightforward in concept but frequently miscalculated in practice. These are the most common errors:

1. Including debt service in operating expenses. Mortgage payments are a financing cost, not an operating expense. NOI is an unlevered metric by definition. Including debt service conflates property performance with the owner’s capital structure and makes the property appear less profitable than it actually is.

2. Using gross income instead of effective gross income. Potential gross income assumes 100% occupancy and full collection. A property at 85% occupancy earns 15% less than its PGI suggests. Always deduct vacancy and collection losses before calculating NOI.

3. Omitting the management fee for self-managed properties. Institutional underwriters always include a market-rate management fee (typically 3–8% of EGI) regardless of whether the current owner self-manages. Without it, NOI is artificially inflated and the property cannot be fairly compared to professionally managed alternatives.

4. Including capital expenditures in operating expenses. Replacing a roof or a building’s HVAC system is a capital expenditure, not an operating expense. CapEx is deducted below the NOI line when computing PBTCF. Mixing CapEx into operating expenses understates NOI and misrepresents operating efficiency.

5. Using the wrong NOI basis for the task. Pro forma (stabilized) NOI is the right input when comparing properties or running cap rate valuations. Trailing-12-month NOI is the right input when underwriting current performance for a loan or acquisition. Using a stabilized NOI for a building in lease-up, or applying trailing NOI to a market cap rate, produces misleading results.

6. Netting expense reimbursements inconsistently. Under NNN and expense-stop leases, tenant reimbursements for CAM, property taxes, and insurance should be added to revenue (as part of EGI), not netted against operating expenses. Netting them against expenses understates both revenue and expenses, which can distort the operating expense ratio and make cross-property comparisons unreliable.

Limitations of NOI as a Performance Metric

1. Does not capture financing costs. Two investors buying identical properties at identical NOI will earn very different equity returns depending on their leverage and interest rates. NOI cannot distinguish between these outcomes because it is calculated before any debt service.

2. Ignores capital expenditure needs. NOI makes a new Class A building and a 40-year-old building with deferred maintenance look equally profitable if they have the same operating income — even though the older building requires substantially more CapEx to maintain its income stream.

3. Single-period snapshot. NOI reflects one year of operations. It does not capture rent growth trajectories, upcoming lease expirations, or planned renovations that will change the income profile. A full DCF proforma is needed to capture multi-year dynamics.

4. Varies by accounting treatment. NOI can differ depending on whether the owner uses cash-basis or accrual-basis accounting, how reserves are classified, and whether replacement reserves are included above or below the NOI line. Always confirm the NOI definition when comparing properties from different sources.

5. Vacancy assumptions can mask risk. Using a stabilized vacancy rate (e.g., 5%) can obscure properties with structural vacancy problems. Older buildings in markets with declining demand may face sustained vacancy well above the stabilized rate. Thorough real estate market analysis reveals whether vacancy is cyclical or structural, and understanding space and asset market dynamics helps forecast how vacancy will evolve.