Real Estate Tax Calc
The formula
NOI = Gross Potential Rent − Vacancy and Credit Losses − Operating Expenses. Operating expenses include property taxes, insurance, property management fees, maintenance and repairs, utilities paid by the owner, and capital expenditure reserves. What is explicitly excluded from NOI: mortgage principal and interest, depreciation, income taxes, and capital improvements. NOI measures the property's performance independent of how it's financed.
How NOI is used
Cap rate = NOI ÷ Property Value. If a property generates $60,000 of NOI and sells for $1,000,000, the cap rate is 6%. Cap rate lets investors compare properties on a financing-agnostic basis — a useful metric when market participants pay cash or use similar leverage.
Valuation: commercial property is often valued by dividing expected NOI by a market cap rate (the income approach). A building with $100,000 NOI in a 5-cap market is worth about $2,000,000. Changes in NOI directly affect value, which is why adding a unit or raising rents has an outsized impact on a building's sale price.
NOI vs. cash flow
NOI is not the same as cash flow. Cash flow subtracts debt service (mortgage principal and interest) from NOI. A property with $60,000 NOI and $48,000 in annual mortgage payments generates $12,000 in annual pre-tax cash flow. Using cash-on-cash return, that $12,000 is divided by total cash invested (down payment, closing costs, renovations) to measure the return on equity.
A line-by-line NOI worked example
Consider a small apartment building with four units renting for $1,500 each — $72,000 of gross potential rent per year. Assume a 5% vacancy and credit loss ($3,600), giving effective gross income of $68,400. Now subtract operating expenses: property taxes $9,000, insurance $3,200, property management at 8% of collected rent ($5,472), repairs and maintenance $4,800, water and trash $3,600, and a capital-reserve allowance of $4,000. Total operating expenses are $30,072.
NOI = $68,400 − $30,072 = $38,328. Notice what never entered the calculation: the mortgage, depreciation, and income taxes. If a lender or appraiser applied a 6.5% market cap rate, this NOI would imply a value of roughly $38,328 ÷ 0.065 ≈ $590,000. Change the assumptions — cut vacancy to 3%, or trim management to 6% — and NOI, and therefore the implied value, both move. That sensitivity is why serious buyers scrutinize every expense line rather than taking a seller's summary at face value.
What belongs in operating expenses — and what doesn't
Operating expenses are the recurring costs of keeping the property running and rentable: property taxes, insurance, management, routine repairs and maintenance, owner-paid utilities, landscaping and snow removal, HOA dues, licensing, and marketing to fill vacancies. A reserve for future capital expenditures (roof, HVAC, parking lot) is commonly included in an underwriting NOI even though it is not a current cash outlay, because ignoring it flatters the number.
Deliberately excluded from NOI are financing costs (mortgage principal and interest), depreciation and other non-cash tax items, income taxes, and one-time capital improvements that are capitalized rather than expensed. Owner-specific costs — your personal travel to check on the property, or asset-management fees you pay yourself — are also typically left out so the metric reflects the asset, not the owner. The goal is a financing- and owner-neutral measure that lets two buildings be compared on equal footing.
NOI is not taxable income — they are two different numbers
A common mistake is treating NOI as the figure you pay tax on. They diverge sharply. NOI excludes two of the largest items on a rental tax return: mortgage interest (deductible for tax, but excluded from NOI because it is financing) and depreciation (a large non-cash deduction that has no place in NOI). As a result, a property can show healthy positive NOI yet report a tax loss on Schedule E once interest and depreciation are subtracted.
The reverse can also happen late in a mortgage's life, when interest is low and depreciation has partly run out: taxable income can exceed cash flow. NOI answers "how well does this asset perform operationally?" while taxable income answers "what does the IRS charge me this year?" Keep the two ledgers separate — confusing them leads to both bad underwriting and bad tax planning.
How lenders use NOI: DSCR and debt yield
Commercial lenders lean on NOI more than almost any other figure. The Debt Service Coverage Ratio (DSCR) = NOI ÷ annual debt service; most lenders want at least 1.20–1.25, meaning NOI must exceed the mortgage payment by 20–25%. In the example above, $38,328 of NOI against, say, $30,000 of annual debt service is a 1.28 DSCR — bankable. Debt yield = NOI ÷ loan amount, a leverage-independent gauge lenders use to size loans (a common floor is around 8–10%).
Because loan proceeds scale with NOI, even a modest, durable increase in NOI can meaningfully raise how much a lender will advance — and how much a buyer can pay. This is the mechanism behind "forcing appreciation": operational improvements that lift NOI translate directly into borrowing capacity and sale value.
Increasing NOI to force appreciation
Because commercial value is NOI divided by a cap rate, raising NOI by a dollar can raise value by many dollars. At a 6% cap rate, each extra $1,000 of annual NOI adds roughly $16,700 of value ($1,000 ÷ 0.06). Landlords pursue this on both sides of the equation: increasing income (raising below-market rents to market, adding a laundry or storage income stream, billing back utilities through RUBS) and reducing controllable expenses (appealing property-tax assessments, re-bidding insurance, cutting management inefficiency).
This is the core of the value-add strategy. A building bought at a 7% cap on $40,000 of NOI ($571,000) that is improved to $52,000 of NOI and sold at a 6% cap is worth about $867,000 — a large gain driven by $12,000 of NOI, not by market movement. It also cuts the other way: deferred maintenance and rising expenses erode NOI and value just as quickly, which is why sophisticated buyers verify a seller's numbers against the actual trailing-12-month statements.
Pro forma vs. actual: read the trailing twelve months
Sellers often market a property on a pro forma NOI — what the building could earn at full occupancy and market rents with optimistic expenses. Actual NOI, drawn from the trailing twelve months (T-12) of real operating statements, is usually lower. The gap between pro forma and actual is where buyers get burned: paying today for income that does not yet exist.
Prudent underwriting rebuilds NOI from the rent roll and the T-12, normalizes for one-time items, and inserts realistic vacancy, management, and capital-reserve figures even if the current owner self-manages and books nothing for reserves. If the numbers only work on the seller's pro forma, the deal is a bet on execution, not a purchase of in-place cash flow — a distinction worth being honest with yourself about before signing.
Gross, net, and modified-gross leases change how NOI compares
Two buildings with identical rents can have very different NOI depending on the lease structure. Under a gross lease, the landlord pays operating expenses out of the rent, so gross-lease rents look high but NOI is thinner. Under a triple net (NNN) lease, tenants pay taxes, insurance, and maintenance directly, so the landlord's stated rent is lower but nearly all of it drops to NOI. A modified gross lease splits the difference, often with the landlord covering some expenses and the tenant reimbursing others through expense stops or CAM charges.
This matters when you compare properties or cap rates across a market: a 6% cap on an NNN building is not the same risk or cash profile as a 6% cap on a gross-lease building, because the expense responsibility — and the exposure to rising taxes and insurance — sits with different parties. Always confirm which lease type underlies a quoted NOI before treating two deals as comparable.
Common ways NOI gets overstated
Because value and loan size both scale with NOI, there is a persistent incentive to inflate it. Watch for these tells in a seller's package: vacancy assumed below market (or at 0%), no management fee booked on an owner-managed building, no capital-reserve line, expenses that omit a recent property-tax reassessment (taxes often jump after a sale resets the assessed value), one-time income counted as recurring, and 'market' rents applied to units currently leased below market. Each of these quietly lifts NOI and, at market cap rates, adds tens of thousands of dollars of apparent value.
The defense is mechanical: rebuild NOI yourself from verifiable documents — the actual rent roll, trailing-12 operating statements, the current tax bill (and an estimate of the post-sale reassessment), and real insurance quotes. An NOI you can defend line by line is worth far more than an impressive number you cannot trace to source records.
Frequently asked questions
Does NOI include mortgage payments?
No. NOI is calculated before debt service. It measures the property's income independent of financing. Subtract mortgage principal and interest from NOI to get pre-tax cash flow.
How is NOI used to value commercial property?
Divide the expected NOI by the market cap rate to estimate property value (income approach). Lower cap rates mean higher valuations for the same NOI.
What is the difference between NOI and cash flow?
NOI excludes debt service; cash flow subtracts it. A high-NOI property with heavy debt service may produce less cash flow than a lower-NOI property with less leverage.
Is NOI the same as my taxable rental income?
No. NOI excludes mortgage interest and depreciation, both of which are deductible for tax. A property can show positive NOI while reporting a tax loss on Schedule E once interest and depreciation are subtracted.
Should NOI include a capital expenditure reserve?
In careful underwriting, yes. Even though a reserve is not a current cash payment, omitting it overstates NOI because roofs, HVAC, and parking lots eventually need replacement. Some brokers exclude it to make a deal look stronger — normalize it back in.
If I manage the property myself, do I still subtract a management fee?
For a true, comparable NOI, yes — include a market management fee (typically 6–10% of collected rent) even when self-managing. Your time has value, and a future buyer or lender will underwrite the fee whether or not you pay it today.
How much can increasing NOI raise a property's value?
At a given cap rate, value equals NOI divided by that rate. At a 6% cap, each extra $1,000 of annual NOI adds about $16,700 of value, which is why raising rents or cutting expenses has an outsized effect on commercial valuations.
Sources
Educational information and estimates only. Not tax advice. Tax rules change and vary by situation; consult a qualified tax professional before acting.