If you own, are buying, or are financing commercial real estate, Net Operating Income is the number that everything else depends on. Your DSCR is derived from NOI. Your cap rate is derived from NOI. Your loan sizing is constrained by NOI. And the value of the property itself is largely determined by NOI.

Most property owners have a general sense of what their property generates. Fewer know their actual NOI — which is why lenders and appraisers often arrive at a different number than the owner expects.

The NOI Definition

Net Operating Income is the income a property generates after subtracting all operating expenses, but before subtracting debt service (mortgage payments), income taxes, and depreciation.

NOI = Gross Potential Income − Vacancy Loss − Operating Expenses

What NOI is NOT:

• Cash flow (cash flow subtracts debt service from NOI)
• Net income (net income subtracts taxes and depreciation)
• Gross revenue (gross revenue doesn't subtract expenses)

This distinction matters enormously in underwriting. Lenders use NOI specifically — not cash flow, not net income — because NOI reflects the property's earning power independent of how it's financed or taxed.

Step-by-Step NOI Calculation

Step 1: Gross Potential Income (GPI)
The total annual rent if all units were 100% occupied at current market rates. For a 10-unit building with average rents of $1,500/month: $1,500 × 10 × 12 = $180,000 GPI.

Step 2: Subtract Vacancy and Credit Loss
Even if the property is fully occupied, lenders apply a stabilized vacancy allowance — typically 5–10% for residential multifamily, up to 15–20% for retail or office. This normalizes for periods between tenants and non-payment.

$180,000 GPI × 5% vacancy = $9,000 vacancy allowance
Effective Gross Income: $180,000 − $9,000 = $171,000

Step 3: Add Other Income
Laundry, parking, storage, late fees, and other property revenue beyond base rent.

$171,000 + $4,800 laundry = $175,800 Effective Gross Income

Step 4: Subtract Operating Expenses
All costs required to operate the property — but not debt service or depreciation.

Typical operating expenses:

• Property taxes
• Insurance
• Property management (8–10% of gross rents — even if self-managed, lenders include this)
• Repairs and maintenance
• Utilities paid by landlord
• Landscaping and janitorial
• Reserves for replacement ($200–$400/unit/year for multifamily)
• Administrative costs

Total operating expenses: $85,000

Step 5: NOI
$175,800 − $85,000 = $90,800 NOI

Why Lenders Calculate NOI Differently Than Owners

This is one of the most common points of friction in commercial real estate underwriting. Owners calculate NOI in ways that favor a higher number; lenders adjust for risk.

Management fee: Self-managing owners often exclude the management fee, arguing they manage it themselves. Lenders always include market-rate management (8–10%) because they need to know what the property generates if management is professional or changes.

Vacancy: A 100% occupied property's owner may use actual vacancy (0%). Lenders use stabilized vacancy (5–10%), which is the long-run expected average.

Reserves: Many owners don't budget capital reserves. Lenders always include them because capital expenditures (roofs, HVAC, appliances) are a real and recurring expense.

Below-market rents: If existing leases are below market, lenders may use market rents in their NOI calculation — or may use actual rents, depending on lease terms. Long-term below-market leases reduce lender confidence in near-term income growth.

The result: a lender's NOI calculation is almost always lower than the owner's. Understanding this gap — and what drives it — prevents surprises in underwriting.

NOI and Cap Rate

NOI is also the foundation of cap rate calculations that real estate investors use to evaluate a property's value.

NOI is the numerator in the cap rate formula:

Cap Rate = NOI ÷ Property Value

Or rearranged to find value:

Property Value = NOI ÷ Cap Rate

A property generating $90,000 NOI in a market where comparable properties sell at an 7% cap rate is worth approximately $90,000 ÷ 0.07 = $1,285,714.

This is how commercial appraisers and investors value income-producing properties. It's also why small differences in NOI create large differences in value: every $10,000 increase in NOI at a 7% cap rate adds $142,857 in property value.

NOI and DSCR

For investment property loans, DSCR is calculated using the property's NOI:

DSCR = NOI ÷ Annual Debt Service

$90,800 NOI ÷ $72,000 annual debt service = 1.26 DSCR — just above the 1.25 minimum required by most lenders.

A lower NOI (due to higher vacancy, higher expenses, or lower rents) would push DSCR below 1.25, limiting loan size or leading to denial.

NOI for Business Owner-Occupants

For owner-occupied commercial real estate (not investment property), lenders use the business's cash flow — not the property's rental income — as the equivalent of NOI for DSCR calculations. The property doesn't generate third-party rental income; the business does. See our full DSCR guide for details.

When you're ready to apply for property financing based on your NOI projections, submit your commercial real estate loan application and work with lenders who understand income-based underwriting.

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