Net operating income is the foundational number in real estate analysis. Every other metric that matters — cap rate, DSCR, cash on cash return — is built on top of it. Get NOI wrong and every downstream calculation is wrong too.
The formula is short. The inputs are where investors consistently make mistakes. Here is the formula, the full expense build, the most common ways NOI gets inflated, and how NOI connects to the three metrics lenders and buyers actually use to screen deals.
Effective Gross Income = Gross Rents − Vacancy & Credit Loss. Operating Expenses = all costs to operate the property. NOI is a pre-financing, pre-tax number. It measures what the property earns on its own, before any mortgage payment enters the picture.
Gross rents are what the units would generate at 100% occupancy. Vacancy & credit loss accounts for the reality that units sit empty between tenants and some tenants pay late or not at all. A standard SFR vacancy assumption is 5–8%; multifamily in strong markets often runs 5%, weaker markets 8–12%.
Operating expenses are every recurring cost to run the property. Below is the standard expense stack for a single-family rental, followed by what most investors leave out.
The exclusions are structural, not optional. Mortgage payments are excluded because NOI is a property-level metric — it has to be independent of financing so two buyers can compare the same deal regardless of their down payment or loan terms. Depreciation is a non-cash tax deduction, not a real cash cost. Income taxes are personal — they vary by the owner’s tax bracket and situation. None of these belong in the analysis of what the property itself produces.
A $300,000 single-family rental in a secondary market. Monthly rent of $2,500. Here is the complete NOI build, line by line.
| Line Item | Annual Amount |
|---|---|
| Income | |
| Gross Rental Income | $30,000 |
| Vacancy & Credit Loss (5%) | −$1,500 |
| Effective Gross Income (EGI) | $28,500 |
| Operating Expenses | |
| Property Taxes | $4,500 |
| Insurance | $1,500 |
| Maintenance & Repairs | $2,500 |
| Property Management (8% of EGI) | $2,280 |
| Capital Reserves | $1,220 |
| Total Operating Expenses | $12,000 |
| Net Operating Income (NOI) | $16,500 |
Expense ratio: $12,000 ÷ $28,500 = 42.1% of EGI. This is in the normal range for a single-family rental — industry experience puts SFR expense ratios at 35–50% depending on age, condition, and local tax burden. If your expense ratio comes in under 30%, you are almost certainly missing something.
Most investors who publish inflated cap rates are not lying — they are building NOI without property management and capital reserves. These are the two most commonly omitted expense lines.
Same property. Two different NOI calculations. When management (8% = $2,280) and capital reserves ($1,220) are omitted from the expense stack, NOI rises from $16,500 to $20,000 — a 21% overstatement. The cap rate rises from 5.5% to 6.7%. The property has not changed. The analysis is wrong.
This matters in practice because:
The standard for rigorous underwriting: include management even if you self-manage, and include reserves even if you plan to defer repairs. The goal is to see what the property actually costs to own, not what it costs to own it optimistically.
NOI is an input to every downstream calculation. Once you have it, three metrics determine whether the deal works.
On the example above: $16,500 ÷ $300,000 = 5.5%. This is the property’s unlevered yield — what it earns per dollar of purchase price before any mortgage enters the picture. Cap rate is used to compare deals across markets and property types, and to back-solve for maximum purchase price at a required yield.
Most conventional lenders require DSCR ≥ 1.20–1.25x. At 1.25x, the property must generate 25% more NOI than its annual mortgage payment. DSCR loans (non-QM investor products) typically require 1.10–1.20x.
Here is where the 2026 rate environment creates a real problem for buyers at 5–6% cap rates. Using the worked example: $300,000 purchase, 25% down ($225,000 loan), at 7.25% for 30 years.
| Item | Amount |
|---|---|
| NOI | $16,500 |
| Monthly mortgage payment ($225K at 7.25%, 30yr) | $1,535 |
| Annual debt service | $18,419 |
| DSCR ($16,500 ÷ $18,419) | 0.896x — FAILS |
The property generates less income than it costs to service the debt. The deal fails the lender’s test at standard 25% down. This is not a broken example — it is the actual math on a typical Class B SFR in 2026. Knowing this early is valuable: it tells you exactly what needs to change before you make an offer.
Two paths to a workable deal:
The practical implication: In a 7%+ rate environment, a 5.5% cap rate at 25% down does not pencil on DSCR. Buyers either accept lower leverage (more cash in), negotiate a lower purchase price, or look for properties with higher NOI relative to price — which means accepting either more risk (Class C) or less competition (tertiary markets).
Annual pre-tax cash flow = NOI − Annual Debt Service. Total cash invested = down payment + closing costs + initial repairs. CoC measures the return on your equity after the mortgage is paid — the number that tells you what your cash is actually earning.
On the example above, the NOI of $16,500 is already below the $18,419 annual debt service, meaning the deal produces negative cash flow at these terms. Cash on cash return would be negative. This is not unusual in 2026 for 5–6% cap rate markets at current rates — it is why many investors have moved to higher-yield markets or are waiting for rates to ease before underwriting new acquisitions.
The Deal Analyzer builds NOI from your inputs, calculates cap rate, DSCR, and CoC, runs sensitivity tables across purchase price and vacancy assumptions, and delivers a GO/NO-GO verdict. Lite $9 / Pro $29.
Get Lite — $9 See Pro — $29What is net operating income (NOI) in real estate?
Net operating income is the income a rental property generates after operating expenses, before any mortgage payments or income taxes. The formula is: NOI = Effective Gross Income minus Operating Expenses. Effective Gross Income is gross rents minus vacancy. Operating expenses include property taxes, insurance, maintenance, property management, and capital reserves. What operating expenses do NOT include: mortgage principal and interest, depreciation, and personal income taxes. NOI is a pre-financing, pre-tax number — it measures how the property performs on its own, independent of how you chose to finance it.
Does NOI include mortgage payments?
No. Mortgage payments — both principal and interest — are excluded from NOI. This is by design. NOI measures the property’s income-generating ability independent of financing. Two buyers could purchase the same property at the same price with very different down payments, loan amounts, and rates. Including debt service would make their NOI different even though the property is identical. NOI is a property-level metric. Cash flow after debt service (what you actually deposit) is a separate calculation, and it is what cash on cash return is based on.
What is a good NOI for a rental property?
There is no universal dollar threshold for “good” NOI — it only means something when expressed as a ratio to purchase price (cap rate) or compared to debt service (DSCR). A $16,500 NOI on a $300,000 property yields a 5.5% cap rate, which is reasonable for a Class B rental in most markets. That same NOI fails the lender’s DSCR test at 7.25% rates with 25% down. A useful benchmark: NOI should exceed your annual mortgage payment by at least 20–25% to clear typical lender requirements.
What is the difference between NOI and net income?
NOI and net income are different. NOI is a real estate metric: it stops at operating expenses and does not deduct mortgage interest, depreciation, or income taxes. Net income (in accounting) deducts all of those — it is what a business reports after taxes. For rental analysis, NOI is the standard because it lets investors compare deals across different financing structures. Net income on a rental varies based on your tax bracket, depreciation schedule, and leverage, making it a poor comparison tool. When lenders, appraisers, and investors discuss “the income from a property,” they mean NOI.