What is NOI in Real Estate?
NOI (Net Operating Income) is the annual income a property generates after deducting all operating expenses, but before mortgage payments and income taxes. It is the single most important metric for evaluating income-producing real estate because it measures the property's ability to generate income independent of how it is financed or how the owner is taxed. Two investors can buy the same property with different loan terms and tax situations, but the NOI remains the same -- making it the standard basis for comparison across all investment properties.
The formula: NOI = Gross Rental Income - Vacancy Allowance - Operating Expenses
What counts as an operating expense
Property taxes, insurance premiums, property management fees (typically 8-12% of gross rent), maintenance and repairs, utilities paid by the landlord, HOA fees, landscaping, pest control, and advertising/leasing costs. These are the recurring costs of operating the property on a day-to-day basis. Operating expenses typically run 35-50% of gross income for residential rentals, though the exact ratio depends on the market, property age, and management structure.
What does NOT count
Mortgage payments (both principal and interest), capital expenditures (new roof, HVAC replacement, major renovations), depreciation, and income taxes. These are financing decisions, improvement investments, or tax accounting items -- not operating costs. The reason mortgage payments are excluded is that NOI must be financing-neutral: it shows what the property earns regardless of whether it was purchased with cash, a conventional loan, or hard money.
Quick example: A rental collecting $2,000/month ($24,000/year) with 5% vacancy ($1,200) and $9,000 in operating expenses has a NOI of $24,000 - $1,200 - $9,000 = $13,800.
Why NOI matters
NOI is used in three critical calculations that drive investment decisions:
- Property valuation (income approach): Value = NOI / Cap Rate. A property with $13,800 NOI in a 7% cap rate market is worth approximately $197,000.
- Cap rate calculation: Cap Rate = NOI / Purchase Price. This allows direct comparison between properties of different sizes and prices.
- Debt Service Coverage Ratio (DSCR): DSCR = NOI / Annual Mortgage Payment. Lenders require a DSCR of 1.2x or higher, meaning the property's NOI must exceed its debt service by at least 20%.
NOI is the standard metric that investors, appraisers, and lenders use to evaluate income-producing real estate. Increasing NOI -- through higher rents, lower vacancy, or reduced operating costs -- directly increases property value, making it the primary lever for value-add investment strategies.