Net Operating Income (NOI)
NOI is what a rental property earns after vacancy and operating expenses, before any mortgage payment. It is the single most important number in rental property analysis — cap rate, DSCR, and value are all derived from it. If NOI is wrong, everything downstream is wrong.
What NOI includes and excludes
| Included (deducted from gross rent) | Not included |
|---|---|
| Vacancy and credit loss | Mortgage principal |
| Property taxes | Mortgage interest |
| Insurance | Income taxes |
| Maintenance and repairs | Depreciation |
| Property management fees | Capital improvements |
| Capital reserves | Debt service of any kind |
The exclusion of debt service is intentional. NOI measures the property's operating performance independent of how it is financed. Two identical properties with different loan structures produce the same NOI — debt affects cash flow, not NOI.
The formula
Or equivalently:
Where Effective Gross Income = Gross Rent − Vacancy Loss.
Worked example
A $160,000 single-family rental with $1,800/month in rent.
| Line item | Annual amount | Notes |
|---|---|---|
| Gross scheduled rent | $21,600 | $1,800 × 12 |
| Vacancy (8%) | − $1,728 | Census vacancy rate for the market |
| Effective gross income | $19,872 | |
| Property taxes | − $2,600 | Verify with county assessor |
| Insurance | − $1,100 | Landlord policy, not homeowner |
| Maintenance | − $1,600 | Ongoing repairs; budget 1% of value/yr |
| Property management (9%) | − $1,944 | On gross rent |
| Capital reserves (5%) | − $1,080 | Future roof, HVAC, appliances |
| Total operating expenses | − $8,324 | |
| NOI | $11,548 |
$11,548 NOI on a $160,000 purchase = 7.2% cap rate.
What the number tells you
NOI answers the question: "Does this property earn enough to cover operating costs and still produce income?" It does not answer whether that income is enough to cover the mortgage.
Use NOI to:
- Calculate cap rate: NOI ÷ Purchase Price
- Calculate DSCR: NOI ÷ Annual Debt Service
- Verify value: if comparable properties trade at 7% cap rates, NOI ÷ 0.07 gives you the implied market value
- Compare properties on equal footing regardless of financing
Common mistakes
1. Starting with the seller's NOI. Seller pro formas routinely understate vacancy, exclude management fees, or skip capital reserves. Always rebuild NOI from scratch using your own assumptions.
2. Using gross rent instead of effective gross income. Gross rent assumes 100% occupancy. A property that sits vacant for one month per year has 8.3% vacancy — roughly $1,800 in lost income on a $1,800/month rental. That is real money.
3. Excluding capital reserves. Properties need new roofs, HVAC systems, and appliances. A 5% capital reserve line ($1,080/year on this example) is not conservative — it is realistic. Omitting it inflates NOI and overstates performance.
4. Using property management fee as a percentage of NOI. Management fees are typically 8–12% of collected rent (or gross rent), not of NOI. If you self-manage, include the fee anyway — that is what a future sale buyer will underwrite to.
How NOI connects to other metrics
| Metric | Uses NOI how |
|---|---|
| Cap rate | NOI ÷ purchase price |
| DSCR | NOI ÷ annual debt service |
| Property value (income approach) | NOI ÷ market cap rate |
| Cash flow | NOI − annual debt service |
NOI is the input to all of these. If you are comfortable with your NOI figure, the rest flows from it.
Where it fits in your workflow
Before modeling any return metric:
- Get the asking price and rental income data
- Apply a realistic vacancy rate (use census data, not the seller's figure)
- List all operating expenses — taxes, insurance, maintenance, management, reserves
- Subtract vacancy and expenses from gross rent to get NOI
- Use NOI to calculate cap rate and DSCR
- Subtract debt service from NOI to get cash flow
If any expense line seems low or missing, adjust it before proceeding.
Frequently asked questions
Does NOI include the mortgage payment? No. NOI is calculated before debt service. Mortgage payments affect cash flow, not NOI. This is by design — it lets you compare properties regardless of how they are financed.
Is NOI the same as profit? No. NOI does not account for mortgage payments, income taxes, or depreciation. After subtracting debt service from NOI you get cash flow. After accounting for taxes and depreciation you get after-tax return — a separate and more complex calculation.
What is a typical expense ratio for a rental property? Roughly 35–50% of gross rent, depending on property type, age, management arrangement, and market. The 50% rule estimates total operating expenses at 50% of gross rent as a quick screen. For actual underwriting, itemize every line.
Should I include property management if I self-manage? Yes. Self-managing is a job. If you stop self-managing or sell the property, a buyer will deduct management fees. Including it in NOI gives you a more honest picture of the property's economics and prevents you from overvaluing a property based on your personal labor.
What if the property has additional income (laundry, parking, storage)? Add it to effective gross income before subtracting operating expenses. Other income can meaningfully improve NOI, particularly for multifamily properties.
NOI is an analytical metric, not investment advice. Returns shown are illustrative. Always verify inputs with current market data and consult qualified professionals before making investment decisions.