The NOI formula
NOI = effective gross income − operating expenses. Effective gross is scheduled rent minus vacancy plus misc income (laundry, parking, pets). Operating expenses are taxes, insurance, repairs, management, utilities you pay, and HOA, never the mortgage, never income tax, never depreciation.
The two classic exclusions stay out because they are not operations: your mortgage payment is financing, and income tax deductions like depreciation belong to your tax return, not the building. Legal costs count; loan costs never do.
The formula rewards precision because a small error compounds through every metric built on it. A $1,200 expense you forget does not just shave $1,200 off NOI. At an 8% cap it also erases $15,000 of appraised value, and at a 1.25× coverage line it can be the difference between a loan that clears and one that does not. The formula is simple; the discipline is counting everything that belongs in it and nothing that does not.
Worked example
A $3,000-a-month duplex grosses $36,000 a year. On this calculator the expense field carries vacancy too, so enter $10,800: $1,800 of vacancy (5% of rent) plus $9,000 in taxes, insurance, maintenance, and management. NOI is $25,200, an 8.4% cap on $300,000. Change one input and every downstream metric moves.
The $10,800 breaks down as $1,800 vacancy, $4,200 taxes, $1,800 insurance, $1,500 maintenance, and $1,500 to a management company. A rent bump or a re-shopped insurance quote moves every downstream metric with it.
Worked example 2: the seller's NOI vs your rebuilt NOI
NOI is only as honest as the expense assumptions behind it, and the seller's sheet is a lead, not a number. A duplex lists at $320,000 with a claimed NOI of $26,400, an 8.3% cap that looks like the deal of the month. The seller's sheet shows $36,000 of gross rent against $9,600 of expenses, and stops there.
Rebuild it line by line with market-realistic figures. Gross rent $36,000. Vacancy at 5% removes $1,800, leaving effective gross income of $34,200. Now the real expense stack: taxes $4,800, insurance $1,800, maintenance at $1,500 per unit for $3,000, management at 9% of effective gross for $3,078, and a capex reserve of $1,200. That is $13,878 of operating expenses the seller's sheet either minimized or left off.
Your rebuilt NOI is $34,200 minus $13,878, so $20,322. On the $320,000 price that is a 6.4% cap, not the 8.3% the listing advertised. Same building, same rent, a $6,000 gap between the two NOI figures, and every dollar of it came from expenses the seller chose not to count.
The lesson is the method, not the math. The seller's NOI is a starting bid in a negotiation, built to make the price look fair. Your rebuilt NOI is the number you underwrite, because it is the only one that survives contact with a vacancy, a tax bill, and a roof. Rebuild it every time, or you are underwriting the seller's optimism.
Case study: the property tax reassessment that killed a deal
Always model property taxes on the new assessed value, not the current one. A buyer pays $480,000 for a fourplex that last sold for $290,000 and is still assessed near that old figure. At closing the taxes are about $4,000 a year, and the buyer underwrites the deal on that number.
The building grosses $48,000 a year and the buyer counts $19,600 of expenses, $4,000 of taxes plus $15,600 for insurance, maintenance, management, and vacancy, leaving an expected NOI of $28,400. On the $480,000 price that is a 5.9% cap, thin but workable for the market.
Then the county reassesses to the new sale price. The assessed value jumps from $290,000 to $480,000 and the tax line resets to about $6,600 a year. The other $15,600 of expenses does not change, so total expenses become $22,200 and the real NOI is $25,800. The cap rate falls to 5.4%, and $2,600 of annual cash flow the buyer counted on simply disappears.
The deal did not get worse; the buyer's numbers did. The building, the rent, and the other expenses never moved. Only the tax line, the one the buyer copied from the seller's current bill instead of modeling on the price actually paid. The lesson: run the reassessment before you close, because the county runs it after.
Why NOI is the number that matters
NOI sets price three ways: appraisers divide market NOI by market cap for value, lenders divide it by debt for DSCR, buyers divide it by price for cap rate. A $1,000 NOI lift at an 8% cap adds ~$12,500 of value, which is why sellers beautify it and you must normalize it.
Watch the beautification kit: added laundry income, ignored vacancy, year-one repairs booked as the norm. Normalize with a fair vacancy (5–8%), full-year maintenance ($1,000–$2,000 per unit), and a market rent you confirm yourself.
The leverage runs in your favor once the building is yours, which is the other half of why the number matters. Cutting $200 a month of owner-paid utilities adds $2,400 of NOI, and at that same 8% cap it creates about $30,000 of value without a single dollar of new rent. Raising rent does the same from the top line. This is the engine behind every value-add deal: find the NOI the seller left on the table, capture it, and let the cap rate multiply the gain into price.
What moves NOI
Rent moves NOI most: a 10% rent gain lifts NOI far more than 10% because expenses stay put. Next come controllable expenses, owner-paid utilities, self-management, insurance shopping. Vacancy is the silent killer: one empty month on $3,000 rent erases $3,000 straight off NOI.
For scale, that 10% rent gain adds roughly $3,600 of NOI on a $25,200 base, and the controllable expenses routinely recover 1–3 points of margin. Small inputs, outsized NOI.
The asymmetry is the point. A rent increase flows to NOI at nearly full margin because taxes, insurance, and the roof do not rise with it, while an expense cut lands dollar for dollar. Either move is small next to the price, and both are large next to the value they create once the cap rate multiplies them, which is why disciplined operators obsess over the expense lines a casual buyer skims past.
A line-by-line expense checklist
Rebuild the seller's sheet line by line: taxes, insurance, utilities you pay, maintenance ($1,000–$2,000 per unit yearly), management (8–10%), vacancy (5–8%), HOA, legal, and turnover. Five lines on their sheet against twelve on yours means yours is the honest one.
Read the fine lines too: reassessment after sale can jump the tax line, always quote insurance instead of trusting the spreadsheet, and budget bad debt, turnover, advertising, and supplies. The calculator field labeled "Annual expenses" expects the full sum of all of it.
The test of a finished sheet is whether a stranger could defend every line. If a number came from the seller, verify it; if it came from your own assumption, write down the source. An NOI you cannot defend line by line is just a guess with a dollar sign, and the appraisal, the loan, and the resale all depend on it holding up.
How appraisers and lenders use your NOI
Value = NOI ÷ cap rate: $25,000 NOI at 8% appraises $312,500; at $22,000 it appraises $275,000. One vacancy plus a furnace vaporized $37,500. Lenders run it backward, requiring NOI to clear the note by 1.25×. Underwrite like both are reading your sheet.
The rest of the machinery: that $3,000 gap also takes a chunk of refinancing proceeds with it, and lenders apply their own vacancy factor to contract rent before deducting expenses. Eventually the appraiser and the lender read the same sheet. Write it for both from the start.
NOI vs. cash flow: the 10-second distinction
NOI and cash flow differ by exactly one line: the mortgage. $25,200 NOI minus $18,200 debt service is $7,000 cash flow, landlord result versus borrower result. A line labeled NOI with the mortgage already subtracted is the fastest sign of a beginner sheet.
Keep them straight in conversations: a lender asking "what's your NOI?" wants the pre-debt figure they underwrite, a partner asking "what does it net you?" wants after-debt. The pro sign is expenses listed before financing, always. Enter both here and the grid shows the full chain: rent, NOI, cap, debt, cash flow.
NOI vs EBITDA vs cash flow: three profit layers, three jobs
These three get used interchangeably and they are not. Each is one step deeper into the money. NOI is property-level, EBITDA is business-level, and cash flow is what the owner actually receives. Confusing them is how a profitable building produces a broke landlord.
NOI, EBITDA, and cash flow each answer a different question about the same dollars. Here is what each one counts, whether debt is in it, and when to reach for it.
| Metric | What it measures | Formula | Includes debt? | When to use |
|---|---|---|---|---|
| NOI | Property operating profit | effective gross income − operating expenses | No | Pricing and comparing buildings |
| EBITDA | Business operating profit | earnings before interest, taxes, depreciation, amortization | No | Valuing an operating company or portfolio |
| Cash Flow | Cash the owner keeps | NOI − debt service | Yes | What actually pays you each year |
NOI prices the building, EBITDA prices the business, and cash flow is the only one that lands in your account.
How NOI treatment differs by property type
NOI is defined the same everywhere, but the inputs vary so much by property type that the same number means different things. Never compare NOI across types on the number alone. Here is how four common types build it differently.
Single-family rentals are the simplest. The expense stack is short: taxes, insurance, maintenance, and vacancy, and the owner usually self-manages, so the management line is often zero on paper. The risk is concentration, one tenant, one vacancy, one income stream, so a single empty month hits NOI at full force.
Small multifamily, two to four units, shares expenses across doors. One roof, one tax bill, one insurance policy spread over several rents, which lifts the margin. The trade is a heavier maintenance load and more turnover, because more units means more leases rolling and more things breaking.
Commercial and larger residential, five units and up, carries the full expense stack. Professional management, capital-expenditure reserves, common-area utilities, and often a marketing line all come out before NOI. The number is more institutional and more honestly burdened, which is why it screens lower than a single-family sheet at the same rent.
Mixed-use splits the difference, allocating expenses between the residential and commercial portions, which often run on different structures entirely. The rule underneath all four: the formula never changes, but what goes into it does, so read every NOI against its own property type's normal expense load before you compare it to another.
The expense ratio is where the types diverge most. A self-managed single-family rental can run a 30 to 35% expense load, a small multifamily closer to 40%, and a fully managed commercial building 45 to 50% or more once management, reserves, and common areas are counted. Two buildings can show the same NOI and have built it from completely different cost structures, which is exactly why the number alone never tells you which is the better deal.
Three NOI mistakes that inflate a deal
Three errors inflate NOI and make a thin deal look strong: putting the mortgage in operating expenses, leaving capital expenditures out entirely, and reading gross rent as NOI. Each one overstates the income the building actually produces. Here is each in real numbers, the cost, and the fix.
Including the mortgage in operating expenses: a building with $34,200 of effective gross and $13,878 of true operating expenses has an NOI of $20,322. Subtract the $18,200 mortgage by mistake and the sheet reads $2,122, a figure that tells you nothing about the building and everything about one loan. The cost is that you can no longer compare properties or price the building cleanly. The fix: NOI stops before debt service, always, because excluding the mortgage is exactly what makes it leverage-free.
Excluding capital expenditures entirely: a landlord books $20,322 as NOI year after year, then a $7,000 roof and a $4,500 HVAC replacement land in the same twelve months. Averaged over a hold, that is roughly $1,200 a year of real cost the NOI never showed, so the honest figure is closer to $19,100. The cost is a return that only exists until the first big system fails. The fix: carry a capex reserve as an operating line, even though lenders and appraisers sometimes leave it below NOI.
Using gross rent as NOI: $36,000 of scheduled rent is not income; it is potential. After $1,800 of vacancy and $13,878 of expenses the real NOI is $20,322, so treating gross rent as NOI overstates the deal by about 78%. The cost is paying a price the income cannot support. The fix: run every building down the full ladder from gross rent to effective gross to NOI, and never stop at the top rung.
The NOI ladder: gross rent to NOI in 5 steps
Most NOI errors come from skipping rungs. Climb all five and the number defends itself: gross scheduled rent, minus vacancy, equals effective gross income; minus operating expenses, equals NOI.
Walk it with the worked example above: $36,000 gross scheduled rent, minus 5% vacancy ($1,800), equals $34,200 effective gross income. Minus $9,000 in operating expenses, equals $25,200 NOI. Same building, same answer. The ladder shows every rung the formula hides. If any rung looks wrong, the NOI is wrong, and so is every cap rate, DSCR, and valuation built on it.
Step 1, gross scheduled rent: every unit at market rent, 100% occupied, plus misc income like parking and laundry. This is potential, not cash. Step 2, vacancy and credit loss: subtract 5–8% for turnover and nonpayment. Skipping this is the classic seller beautification. Step 3, effective gross income: the collectible remainder. Lenders underwrite from here, never from step 1. Step 4, operating expenses: the full stack, where a normal load runs 35–45% of effective gross. Step 5, NOI: the remainder. Divide it by price for cap rate, by debt for DSCR, by units for per-unit comps.
Which calculator to use next
NOI is the input, not the answer. Every return metric divides it, so once you have an honest NOI, push it through the rest of the chain in order. Start with the cap rate calculator to see what the building earns per dollar of price before any loan, which is how you compare it against every other building on the market.
Then test the financing. Run the DSCR calculator to see whether the income covers the note by the 1.25× a lender demands, and the cash-on-cash calculator to see what your actual invested dollars pay after the mortgage. If the plan is to pull capital back out, the BRRRR calculator shows what a cash-out refinance returns. The pattern never changes: get NOI honest first, then let the other metrics divide it. For the whole hold rather than one year, the rental cash flow calculator carries the same income through every year of rent and the sale.
The vacancy rung is where a partial month hides. A turnover on the 20th does not cost a full month of rent, it costs the days between that move-out and the next move-in, and the prorated rent calculator prices those two dates exactly. That is the difference between an allowance that overstates the loss and an NOI that never sees it.
Frequently asked questions
16 answers, no funnel.
What does NOI exclude?
Debt service, income taxes, depreciation, capital improvements (a new roof is an asset, not an operating expense), and any owner draw. Including mortgage payments in expenses is the most common beginner mistake.
How do I estimate NOI for a property with no rent roll?
Use market rents for comparable units, allow 5–8% vacancy, then subtract taxes from public records, insurance quotes, $1,000–$2,000 per unit of maintenance, and 8–10% management if it is tenant-managed.
Is high NOI always good?
NOI must be read against price. $25,000 NOI on a $180,000 house is excellent; the same $25,000 on a $700,000 building is a 3.6% cap. Divide before you celebrate.
Should I count my own management labor as an expense?
Yes if you plan to hire a manager later, yes if the alternative (investing the time elsewhere) has a value. A fourplex that only "works" with free self-management is a job, not a passive return.
How does vacancy hit NOI?
Directly and at full margin. A 7% vacancy on $36,000 of scheduled rent removes $2,520 from effective income and lands dollar-for-dollar in the NOI, which at an 8% cap costs you $31,500 of appraised value.
How do you calculate NOI from cap rate?
Multiply cap rate by value: a $500,000 building at a 6% cap carries $30,000 of NOI. Flip it for value, NOI ÷ cap rate prices the building, which is how appraisers check your math.
NOI vs EBITDA: what is the difference?
NOI is property-level: rent minus operating expenses, before debt, taxes, depreciation, and capex. EBITDA is company-level and adds back interest, tax, depreciation, and amortization across the whole business. Same family, different altitude.
What is an NOI calculator used for?
An NOI calculator turns rent, vacancy, and expenses into NOI, then into cap rate, DSCR qualification, and value estimates. Use it to sanity-check a listing before you underwrite, and to compare buildings on operations alone.
Can NOI be negative?
Yes, when expenses plus vacancy exceed collected rent, NOI goes negative before the mortgage even enters. The building loses money on operations alone; no financing structure fixes that, only higher rent or lower costs.
What is a good NOI margin?
A healthy NOI margin, NOI divided by gross rent, lands between 55% and 70% for residential rentals. Below 50% usually means expenses or vacancy are eating the deal. Above 75% is possible but rare without deferred maintenance.
What vacancy rate should I use when calculating NOI?
Use 5–8% for stable residential rentals and 8–12% for student, seasonal, or high-turnover markets. Never use the seller's quoted vacancy. Pull actual trailing-12-month figures or a local market average.
Is capital expenditure part of NOI?
Usually no. NOI covers operating expenses, and a new roof or HVAC is a capital improvement added to the building's basis. Many investors still carry a capex reserve as an operating line to keep the figure honest.
Does NOI include property management fees?
Yes. Management is an operating expense and comes out before NOI, typically eight to ten percent of collected rent. Even self-managed properties should count it, because your labor has a cost and a future manager will charge it.
How is NOI different from gross rent?
Gross rent is the scheduled total before any costs. NOI subtracts vacancy and all operating expenses, so it is always lower. Gross rent is potential income; NOI is what the building actually earns from operations.
How do you calculate the NOI?
Annual gross rent minus vacancy minus operating expenses. Take $36,000 of rent, subtract $1,800 for vacancy and $12,000 for taxes, insurance, maintenance, and management. NOI is $22,200. The mortgage is never included.
Is NOI calculated per year?
Yes. NOI is always annual. If a property rents for $3,000 a month, the calculator converts that to $36,000 per year before subtracting expenses. Monthly NOI is possible for internal tracking but never used in cap rate or lender math.