What is NOI in rental property investing?

Net Operating Income (NOI) is the annual income a rental property generates after subtracting all operating expenses but before subtracting mortgage payments, depreciation, and capital expenditures. It measures the property's ability to produce income independent of how it is financed. A property collecting $13,800 in annual rent with $5,820 in operating expenses has an NOI of $7,980.

Are mortgage payments included in NOI?

No. Mortgage payments (both principal and interest) are excluded from the NOI calculation. NOI measures property-level performance before financing costs. This allows investors to compare properties on equal footing regardless of down payment size, interest rate, or loan terms. Debt service is subtracted from NOI when calculating cash flow, not NOI itself.

What is a good NOI for a rental property?

There is no universal good NOI because it depends on the property value and market. Instead, investors evaluate NOI through cap rate (NOI divided by property value). A $7,980 NOI on a $150,000 property gives a 5.3% cap rate, which is typical for a stable residential rental. Cap rates above 7% suggest higher returns but often come with higher risk or deferred maintenance. Cap rates below 4% are common in appreciation-focused markets like coastal cities.

What is the difference between NOI and cash flow?

NOI is income minus operating expenses. Cash flow is NOI minus debt service (mortgage payments). A property can have a positive NOI of $7,980 but negative cash flow of negative $636 per year if the annual mortgage payments total $8,616. This happens when high leverage (a large loan relative to property value) produces debt service that exceeds the NOI. The property still operates profitably at the property level, but the financing structure consumes more than it generates.

How do you calculate cap rate from NOI?

Cap rate equals NOI divided by current property value (or purchase price), expressed as a percentage. If the NOI is $7,980 and the property value is $150,000, the cap rate is 5.3%. Cap rate is the return you would earn if you purchased the property with all cash and no mortgage. It is the standard metric for comparing rental properties across different markets, price points, and financing structures.

How to Calculate NOI for Rental Property

Net Operating Income (NOI) equals total rental income minus operating expenses, excluding mortgage payments, depreciation, and capital expenditures. For a property collecting $1,150/month in rent with $5,820 in annual operating expenses, the NOI is $7,980 ($13,800 minus $5,820).

The NOI formula, step by step

NOI is a two-step calculation. First you determine your Effective Gross Income. Then you subtract operating expenses. Mortgage payments, depreciation, and capital improvements never touch this formula.

Gross Rental Income − Vacancy & Credit Loss

= Effective Gross Income (EGI)

Effective Gross Income − Operating Expenses

= Net Operating Income (NOI)

Here is the formula applied to a single-family rental collecting $1,150/month with a property manager charging 10%.

Calculate Gross Rental Income

$1,150/month x 12 months = $13,800 gross rental income. Include all income the property generates: base rent, late fees, pet rent, laundry, parking, or application fees.

Subtract vacancy and credit loss

Most investors use 5% to 8% as a vacancy reserve. For this example with a long-term Section 8 tenant, actual vacancy is near zero. Using actual numbers: $13,800 EGI. If you apply a 5% reserve, EGI drops to $13,110.

Total up operating expenses

Property taxes ($1,800) + insurance ($1,440) + PM fees ($1,380) + repairs ($800) + landscaping ($200) + pest control ($200) = $5,820 in total operating expenses.

Subtract to get NOI

$13,800 minus $5,820 = $7,980 NOI. This is the income the property produces before any mortgage payment, before depreciation, and before capital expenditures.

What counts as an operating expense for NOI

Operating expenses are the recurring costs required to keep the property rented and maintained. They do not include costs related to financing, tax strategy, or one-time capital projects.

Included in NOI (Operating Expenses)	Excluded from NOI
Property taxes	Mortgage payments (principal + interest)
Property insurance	Depreciation
Property management fees	Capital improvements (new roof, HVAC replacement)
Repairs and maintenance	Income taxes
Utilities (if landlord-paid)	Loan origination fees
Landscaping and lawn care	Closing costs
Pest control	Investor salary or owner draws
HOA fees	Reserves set aside for future capex

Common confusion

Mortgage payments are the most frequently misplaced item. They feel like an operating cost because you pay them every month. But NOI measures property performance independent of financing. Two investors can buy the same property with different down payments and loan terms. NOI stays the same. Cash flow does not.

NOI vs. cash flow: same property, different numbers

A property can have a healthy NOI and still produce negative monthly cash flow. This happens when leverage (a large loan) creates debt service payments that exceed the NOI. Here is the math for the same $150,000 property with a $120,000 mortgage at 7.5%.

Line Item	Annual Amount	Calculation
Gross Rental Income	$13,800	$1,150 x 12
Operating Expenses	($5,820)	Taxes + Insurance + PM + Repairs + Other
NOI	$7,980	$13,800 minus $5,820
Debt service (mortgage P&I)	($8,616)	$718/month P&I x 12
Pre-tax cash flow	($636)	$7,980 minus $8,616

Why this matters

The NOI is $7,980. The property operates profitably at the asset level. But the financing structure consumes the entire NOI and then some, producing a $636 annual shortfall in actual cash. This investor is subsidizing the property $53/month out of pocket. The equity paydown on the mortgage ($3,200+ in year one) is building wealth, but it does not help with monthly bills. Understanding the gap between NOI and cash flow prevents surprises after closing.

Cap rate: what NOI tells you about value

Cap rate is NOI divided by property value, expressed as a percentage. It answers one question: what return would this property generate if you paid all cash?

Cap Rate = NOI ÷ Property Value

$7,980 ÷ $150,000 = 5.3%

Cap rate removes financing from the equation. An investor paying $150,000 cash and an investor putting 20% down with a 7.5% mortgage both see the same 5.3% cap rate. The difference shows up in cash-on-cash return, not cap rate.

Cap rate benchmarks by market type

Market Type	Typical Cap Rate	What It Means
Coastal / appreciation markets	3% to 5%	Lower income yield, betting on price growth
Stable suburban / Midwest	5% to 7%	Balanced income and moderate appreciation
High-yield / tertiary markets	7% to 10%+	Higher income, often higher risk or deferred maintenance

When two properties have similar purchase prices, the one with the higher NOI has the higher cap rate. When comparing properties at different price points, cap rate normalizes the comparison so you are evaluating income generation per dollar invested.

Five mistakes that skew your NOI calculation

Including mortgage payments in operating expenses. This is the most common error. Mortgage principal and interest are financing costs, not operating costs. Including them makes NOI look lower than it actually is and makes cap rate comparisons meaningless across properties with different loan structures.

Forgetting to account for vacancy. Using gross rent as if the property will be 100% occupied every month overstates income. Even with a reliable long-term tenant, turnover happens. A 5% vacancy reserve on $13,800 is $690 per year. Skipping this inflates your NOI by that amount and makes the property look healthier than it is.

Using gross rent instead of effective gross income. Gross rent is the starting point, not the income figure. Effective Gross Income accounts for vacancy, credit loss, concessions, and any rent not collected. If a tenant skips a month and you waive a late fee to keep them, your EGI is lower than gross rent.

Excluding PM fees when self-managing. You manage the property today, so PM fees are zero. But if you plan to hire a property manager later (or scale to the point where you have to), your NOI will drop by 8% to 10% of collected rent overnight. Underwriting without PM fees produces an NOI that only works while you are doing the work yourself.

Not annualizing partial-year expenses. If you bought the property in September, you have four months of expenses. Dividing four months of repairs by four does not give you an accurate annual figure. Seasonal costs (heating, landscaping, pest control) cluster in specific months. Use 12 months of historical data from the seller or PM whenever possible.

Full NOI breakdown: example property

Pulling it all together for a $150,000 single-family rental, $120,000 mortgage at 7.5%, renting at $1,150/month with 10% property management.

Category	Annual Amount	Notes
Gross Rental Income	$13,800	$1,150 x 12
Vacancy reserve (5%)	($690)	Conservative estimate
Effective Gross Income	$13,110
Property taxes	$1,800	County assessment
Insurance	$1,440	Landlord policy
Property management	$1,380	10% of collected rent
Repairs and maintenance	$800	Plumbing, filters, minor fixes
Landscaping	$200	Lawn service (seasonal)
Pest control	$200	Quarterly treatment
Total Operating Expenses	$5,820
NOI	$7,290	EGI minus OpEx ($13,110 minus $5,820)
Cap rate	4.9%	$7,290 / $150,000

Without the vacancy reserve, NOI is $7,980 and cap rate is 5.3%. The difference illustrates why two investors analyzing the same property can arrive at different NOI numbers. The assumptions matter. Whichever method you use, be consistent across every property so the comparisons are valid.

How DoorVault tracks NOI automatically

DoorVault calculates real-time NOI per property using actual income and expenses tracked year-round, not projections or estimates from a spreadsheet updated once a quarter.

Per-property NOI on every property detail page, calculated from actual transactions. Updates automatically as new income and expenses are recorded.

Portfolio dashboard shows aggregate NOI across all properties. See which properties carry the portfolio and which ones drag it down.

Property health scores factor in NOI trends over time. A declining NOI triggers visibility so you catch problems before they compound.

Knox AI reads PM statements and bank feeds, auto-categorizes every transaction, and keeps your NOI calculation current without manual data entry.

Deal analyzer calculates projected NOI before you buy, using local market data for taxes, insurance, and rent comps. Compare projected vs. actual NOI after you close.