When it comes to evaluating a commercial property's financial performance, few metrics carry more weight than Net Operating Income, commonly referred to as NOI. Whether you are a seasoned investor analyzing a value-add multifamily deal, a business owner considering an owner-occupied office building, or a lending professional underwriting a commercial mortgage, understanding how to calculate and interpret NOI is an essential skill. It forms the foundation of nearly every commercial real estate valuation method and plays a central role in determining how much financing a property can support.
In today's lending environment, where interest rates have remained elevated through much of 2024 and into 2025, lenders are scrutinizing NOI more carefully than ever. A property with a strong, well-documented NOI can still qualify for favorable financing terms, even in a tighter credit environment. This guide will walk you through exactly how NOI is calculated, what expenses are included and excluded, and how lenders use this figure to make critical loan decisions.
What Is Net Operating Income and Why Does It Matter?
Net Operating Income is the total income generated by a commercial property after all operating expenses have been deducted, but before mortgage debt service, income taxes, and depreciation are factored in. It represents the true earning power of a property on a standalone basis, stripped of financing structure and ownership-specific tax considerations. This makes it an objective benchmark that lenders, appraisers, and investors can use to compare properties on equal footing.
NOI is the primary input used to calculate the capitalization rate, or cap rate, which is used to determine a property's market value. It is also a key component of the Debt Service Coverage Ratio (DSCR), which most commercial lenders require to be at least 1.20 to 1.25 before approving a loan. According to the Mortgage Bankers Association, DSCR remains one of the top three underwriting criteria for commercial real estate loans in 2024 and 2025, alongside loan-to-value ratio and borrower net worth.
According to CBRE's 2025 U.S. Real Estate Market Outlook, income-producing commercial properties with a documented NOI growth of 3% or more year-over-year are commanding capitalization rate compression of 25 to 50 basis points compared to stagnant-income assets in the same submarket.
The Step-by-Step NOI Calculation
Calculating NOI is straightforward once you understand what belongs in each category. The basic formula is: Gross Potential Income minus Vacancy and Credit Loss equals Effective Gross Income, and Effective Gross Income minus Total Operating Expenses equals Net Operating Income. Here is how each component breaks down in practice.
Step 1: Calculate Gross Potential Income (GPI). This is the maximum rental income the property could generate if it were 100% occupied at current market rents. For a 10-unit apartment building where each unit rents for $1,500 per month, the GPI would be $180,000 annually. For retail or office properties, this figure includes base rent, percentage rent clauses, and any other income tied directly to occupancy.
Step 2: Subtract Vacancy and Credit Loss. No property operates at 100% occupancy indefinitely. Lenders and appraisers typically apply a market-based vacancy factor, often ranging from 5% to 10% for stabilized assets, though this varies significantly by market and property type. In markets like downtown San Francisco or Chicago's Loop, office vacancy rates reached historic highs above 20% in 2024, which dramatically affects NOI projections for those assets.
Step 3: Add Ancillary Income. Effective Gross Income also includes non-rental revenue streams such as parking fees, laundry income, storage unit rentals, cell tower lease payments, and vending machine revenue. These figures should be documented with at least two years of operating history when presenting to a lender.
Step 4: Deduct All Operating Expenses. This is where precision matters most. Operating expenses include:
- Property taxes and assessments
- Property and liability insurance premiums
- Property management fees (typically 4% to 10% of collected rents)
- Routine maintenance and repairs
- Utilities paid by the owner (water, sewer, trash, common area electricity)
- Landscaping and janitorial services
- Reserves for replacement (capital expenditure reserves)
- Administrative and accounting expenses
It is critical to note what is NOT included in operating expenses: mortgage principal and interest payments, depreciation, income taxes, and large one-time capital improvements are all excluded from the NOI calculation. Including debt service would make the NOI dependent on the financing structure rather than the property itself, defeating its purpose as an objective valuation tool.
A Practical NOI Example
To illustrate how NOI works in a real-world context, consider a 20,000-square-foot retail strip center in the Dallas-Fort Worth metro area, one of the strongest commercial real estate markets in the country through 2024 and into 2025. Suppose the property is fully leased at an average rate of $18 per square foot annually, producing a Gross Potential Income of $360,000. With a 5% vacancy allowance, Effective Gross Income drops to $342,000. Add $12,000 in miscellaneous income from pylon signage leases, and the property generates $354,000 in total effective income.
Now assume total annual operating expenses break down as follows: $42,000 in property taxes, $14,000 in insurance, $28,000 in property management fees, $18,000 in maintenance and repairs, $9,000 in utilities, and $12,000 in replacement reserves. Total operating expenses come to $123,000. Subtracting this from $354,000 yields an NOI of $231,000. If the prevailing cap rate for similar retail assets in that submarket is 6.5%, the implied property value would be approximately $3.55 million, which directly informs how much debt the asset can support.
How Lenders Use NOI to Underwrite Commercial Loans
When you submit a commercial loan application, the lender's underwriting team will independently verify and often reconstruct your property's NOI from scratch. They will review two to three years of tax returns, rent rolls, operating statements, and lease agreements. It is common for lenders to apply their own stabilized vacancy assumptions and cap their management fee allowances, which can result in an underwritten NOI that differs from the owner's stated figures.
The underwritten NOI is then divided by the annual debt service obligation to produce the DSCR. For example, if a property generates an underwritten NOI of $231,000 and the proposed loan requires annual debt service of $175,000, the DSCR would be 1.32, which comfortably exceeds the 1.25 minimum threshold required by most conventional commercial lenders. A higher DSCR gives the lender confidence that the property can sustain mortgage payments even if income dips or expenses rise unexpectedly.
Different loan programs carry different NOI and DSCR requirements. SBA 504 and 7(a) loans, CMBS conduit loans, bank portfolio loans, and life company loans each have distinct underwriting standards. Working with an experienced commercial mortgage broker ensures that your property's NOI is presented in the most accurate and favorable light for the right loan program, while also managing lender expectations from the outset.
As commercial real estate markets continue to evolve through 2025 and beyond, the ability to accurately calculate, document, and present NOI will remain a defining factor in separating successful loan applications from unsuccessful ones. With shifting rent dynamics in office and retail sectors and continued strength in industrial and multifamily assets, investors who master NOI analysis will be best positioned to identify opportunities, secure financing, and build lasting portfolio value in any market cycle.
