NOI (Net Operating Income): The Engine Behind Every Commercial Valuation
Cap rate, loan sizing, sale price — they all grow from one number: NOI. And it’s exactly where sellers do their makeup. Read every line of the NOI and you’ll know whether you’re buying income or an illusion.
What exactly is NOI and how do you calculate it?
NOI = Effective Gross Income − Operating Expenses. Effective Gross Income = potential rent + other income (parking, signage, recoverables) − vacancy and bad debt. Operating Expenses = property tax, insurance, maintenance, management, common-area utilities. Critically, NOI excludes mortgage interest, depreciation, and capital expenditures (capex). It measures the property’s own operating profit and is the shared starting point for both cap rate and loan sizing.
Source: commercial valuation practice / CRE underwriting standards (2026)
I’m Arthur Zhao. If cap rate is the ruler, NOI is the thing being measured — and it’s the single most manipulated line in the whole deal. The bank sizes your loan off NOI, the valuation sets the building’s worth off NOI, so sellers have every incentive to dress it up. This piece lays out what goes into and out of each NOI line, and how to rebuild the seller’s “ideal” version into a real one.
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Income side: potential vs effective
Expense side: what counts as "operating"
Three things that never belong in NOI
⚠️The sneakiest move: the seller books a management fee of $0 because they self-manage. But once you take over you’ll either hire a manager or spend your own time — a real 3-5% cost that exists in reality. Always add a market management fee back into your NOI when underwriting.
💡 One line to remember: NOI is how much net cash the building throws off in a year assuming no borrowing, no tax depreciation, and no major capital repairs. It’s operating-level earning power. Capex and your mortgage sit outside it, in a separate layer that belongs to your personal financial structure.
The 5 common pro-forma makeup tricks
How to rebuild a real NOI
ℹ️Demand “actual” — not “pro forma” — operating statements for the last 2-3 years, and write it into your offer’s due-diligence condition. A seller who can only produce an optimistic projection, not actuals, is itself a risk signal.
Frequently Asked Questions
What’s the difference between NOI and cash flow?
NOI is operating-level net income, before debt service and capex. Your actual pre-tax cash flow = NOI − mortgage payments (principal + interest) − a capex reserve. So NOI is always at least as large as the cash you actually keep. Don’t mistake NOI for take-home money.
Do recoverables count in NOI?
Yes, but list both sides honestly: recoverable costs billed to tenants go in income, and the matching actual costs go in expenses. In a fully-leased NNN property they roughly cancel; with vacancy, the recoverable share on empty units falls on the owner, genuinely lowering NOI — which is exactly why the vacancy assumption matters so much.
Why is capex excluded from NOI?
Because capex is large and non-recurring (roof, HVAC), and loading it into any single year distorts that year’s operating profitability. Industry practice is to keep NOI clean and carry a separate annual capex reserve deducted in the cash-flow model. But you must never pretend capex doesn’t exist when underwriting.
Should I use the seller’s NOI or my own?
Always use your own conservative NOI rebuilt from actual leases and statements. The seller’s pro forma is a marketing document, not an underwriting basis. The gap between the two NOIs, multiplied by 1/cap rate (e.g. 20× at 5%), is what you could overpay — which is precisely where due diligence earns its keep.
Arthur Zhao
Real Estate Broker · FRI · ABR · SRS · PSA · MCNE · E-PRO · CLHMS & GUILD Elite · REAIS
VP & Branch Manager, Bay Street Group Inc.
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