Net Operating Income (NOI) is the foundation of all real estate valuation. Learn the exact formula, what to include and exclude, and how NOI drives cap rates and property values.

How to Calculate NOI in Real Estate: Net Operating Income Explained

Net Operating Income (NOI) is the most fundamental number in all of real estate investing. Every key metric — cap rate, property valuation, debt coverage ratio — flows directly from NOI. If you get NOI wrong, everything built on top of it is wrong too.

This guide explains exactly what NOI is, how to calculate it, and the common mistakes that lead to inflated NOI figures.

What is NOI?

Net Operating Income is a property's total income minus all operating expenses — but before deducting mortgage payments, depreciation, or income taxes.

NOI = Effective Gross Income − Operating Expenses

The exclusion of mortgage payments makes NOI a property-level metric that's independent of how you finance the deal. That's what makes it so useful for comparing properties and determining value.

Step 1: Calculate Effective Gross Income

Start with all the money the property generates:

Gross Rental Income: Total rent from all units at full occupancy

Other Income:

Parking fees
Laundry income
Storage unit fees
Pet fees
Late fees

Minus Vacancy and Credit Loss: Budget 5–8% of gross rent for vacancy and non-paying tenants.

EGI = (Gross Rent + Other Income) × (1 − Vacancy Rate)

Example:

4-unit building, $1,200/unit/month = $4,800/month gross rent ($57,600/year)
Other income (laundry): $1,200/year
Total potential income: $58,800
Vacancy (6%): −$3,528
Effective Gross Income: $55,272

Step 2: Subtract Operating Expenses

Operating expenses include everything it costs to run the property:

What IS an Operating Expense

Property taxes
Property insurance
Property management fees
Routine maintenance and repairs
Landscaping, snow removal
Utilities (if owner-paid — common areas, water, trash)
HOA dues
Pest control
Advertising/marketing
Legal and accounting fees
License and permit fees

What is NOT an Operating Expense

This distinction is critical:

| NOT Included | Why | |---|---| | Mortgage payment (P&I) | Financing decision, not property operations | | Depreciation | Non-cash accounting item | | Income taxes | Investor-level, not property-level | | Capital expenditures | One-time, not recurring (but CapEx reserves often are included) |

Note on CapEx reserves: Purists exclude CapEx from NOI. Practical investors include monthly reserves ($100–150/unit) as an operating expense. Be consistent and know which convention you're using.

Example operating expenses (continuing from above):

| Expense | Annual | |---|---| | Property taxes | $6,000 | | Insurance | $2,400 | | Property management (8%) | $4,422 | | Maintenance & repairs | $3,600 | | CapEx reserves | $2,400 | | Utilities (common areas) | $1,200 | | Landscaping | $600 | | Miscellaneous | $500 | | Total | $21,122 |

Step 3: Calculate NOI

NOI = EGI − Operating Expenses
NOI = $55,272 − $21,122 = $34,150

Using NOI for Cap Rate and Valuation

Once you have NOI, you can:

Calculate cap rate:

Cap Rate = NOI ÷ Property Value
$34,150 ÷ $500,000 = 6.83%

Value the property using market cap rates:

Property Value = NOI ÷ Market Cap Rate
$34,150 ÷ 0.07 = $487,857

This is how commercial real estate is valued. If the seller is asking $500,000 but your verified NOI and market cap rate suggest $488,000, you have data for negotiation.

Calculate Debt Coverage Ratio (DCR):

DCR = NOI ÷ Annual Debt Service
$34,150 ÷ $28,000 = 1.22

Lenders typically require DCR ≥ 1.25. This deal just barely qualifies.

Common NOI Mistakes

Using Gross Rent Instead of EGI

Always subtract vacancy. A property that's been 100% occupied for years will eventually have turnover.

Accepting Seller-Provided Expense Statements

Sellers routinely understate expenses. Get 3 years of tax returns and verify every line item.

Forgetting CapEx

A property that hasn't had a roof or HVAC replacement in 15 years is accumulating a large future liability. Include reserves.

Ignoring Management Costs

Even if you self-manage, include a management expense (8–10%) in NOI. This ensures the deal pencils if you ever need to hire help, and correctly values your time.

NOI in the Analysis Workflow

Gross Rent + Other Income
  − Vacancy/Credit Loss
= Effective Gross Income (EGI)
  − Operating Expenses
= Net Operating Income (NOI)
  − Debt Service (mortgage payment)
= Net Cash Flow

See our complete guide on how to analyze a rental property to understand how NOI fits into the full analysis.

Calculate NOI Automatically

Run the complete analysis — NOI, cap rate, cash flow, and CoC return — with our free property analysis tool. Enter your numbers once and get all the metrics instantly.

Understanding NOI is step one. See how it drives cap rate and property valuation in our full guide series.