Net operating income is the number every commercial real estate decision runs through. It sets the value under an income approach, it sizes the loan through the debt service coverage ratio, and it is the first figure an investment committee asks about. It is also easy to get wrong, because the operating statement you calculate it from arrives as a PDF and half the lines on it do not belong in the calculation at all.
This walks through building NOI in Excel from a trailing twelve month statement: the formula, the lines that count, the lines that look like they count but do not, and the reconciliation step that catches a mistake before it reaches your model.
How do you calculate NOI?
Net operating income equals effective gross income minus total operating expenses. Effective gross income is gross rental income plus other income, less vacancy loss. Operating expenses are the costs of running the property: taxes, insurance, utilities, repairs and maintenance, management fees, and payroll. Debt service, capital expenditures, and depreciation are excluded, because NOI measures unlevered operating performance before financing.
Written as one line: NOI = (Gross Rental Income + Other Income - Vacancy Loss) - Total Operating Expenses.
That exclusion at the end is the part people trip over. Two buyers looking at the same property with different loans should compute the same NOI, which is only true if financing stays out of it.
What is a T12 in real estate?
A T12, short for trailing twelve months, is an operating statement covering the property's actual income and expenses over the last twelve months. It shows each line item month by month, with an annual total column on the right. Lenders and buyers ask for it because it reports what the property really did, rather than what a pro forma projects it might do.
Because it is a wide grid, twelve monthly columns plus a total, the T12 is the single most annoying document in a deal package to retype. It is also the one you cannot afford to mistype.
Getting the T12 out of the PDF first
You cannot total a PDF. Before any of this works, the statement has to be a spreadsheet with each line item on its own row and the monthly columns intact. Run it through a converter built for operating statements and download the XLSX, or convert the whole package at once if the rent roll and expense schedules came with it. Scanned pages from a seller binder still work, because OCR reads them.
Two things to confirm the moment the file opens. First, the amounts have to be real numbers rather than text, or nothing will sum. Click an amount and look at the formula bar, or select a column of figures and check that the status bar shows a sum. If it does not, the fix is quick: our guide on numbers that come across as text covers it. Second, watch for a repeated header row where the statement broke across pages, which inflates a subtotal in a way that is very hard to spot later.
What is included in operating expenses?
Operating expenses are the recurring costs required to keep the property running and producing income. On a typical multifamily T12 that means property taxes, property insurance, utilities the owner pays, repairs and maintenance, contract services like landscaping and pest control, on-site payroll, general and administrative costs, marketing, and the property management fee.
Two judgment calls come up constantly. Management fees should be normalized to a market rate, often three to four percent of effective gross income, even when the seller self-managed and booked nothing. Repairs and maintenance should be scrubbed for anything that is really a capital item, because a roof replacement sitting in R and M understates NOI and a lender will move it back out.
What is not included in NOI?
Four categories stay out, and each one is on the statement anyway:
| Line | In NOI? | Why |
|---|---|---|
| Mortgage principal and interest | No | Financing, not operations. NOI is unlevered by definition. |
| Capital expenditures | No | Roof, HVAC, unit renovations. These are investments, not operating costs. |
| Depreciation and amortization | No | Non-cash accounting entries with no bearing on operations. |
| Income taxes | No | Owner-level, not property-level. Property taxes do count. |
| Property taxes | Yes | A real, recurring cost of owning and operating the asset. |
| Management fee | Yes | Normalize to market even if the seller self-managed. |
If a seller's statement shows an NOI noticeably higher than yours, this table is usually where the gap lives. Somebody left capital expenditures out of the expense stack, or forgot to charge a management fee.
How do you calculate NOI in Excel?
Once the converted T12 is open, lay it out so the calculation is auditable rather than clever. Keep every source line where the converter put it, then build the rollup below it with formulas that point back at those rows. If a reviewer cannot trace your NOI to a line on the seller's statement in one click, the model is not finished.
A minimal structure on the annual column looks like this:
| Row | Line | Formula |
|---|---|---|
| 1 | Gross Rental Income | from the statement |
| 2 | Other Income | from the statement |
| 3 | Vacancy Loss | entered as a negative |
| 4 | Effective Gross Income | =SUM(B1:B3) |
| 5 | Total Operating Expenses | =SUM(B6:B14) |
| 6 | Net Operating Income | =B4-B5 |
Enter vacancy loss as a negative number so effective gross income is a plain SUM rather than a mix of plus and minus signs you have to reread six weeks from now. Then copy the same formulas across all twelve monthly columns. Monthly NOI is where a property tells on itself: a single soft month of collections, or a spike in repairs in month nine, is invisible in the annual total and obvious in the row.
If the expense lines are scattered rather than contiguous, group them with SUMIF against a category column instead of a hardcoded range. =SUMIF($A:$A,"OpEx",B:B) survives an inserted row. A hardcoded SUM(B6:B14) does not, and that is exactly the kind of silent break that shows up after somebody adds a line at the top.
Is NOI the same as EBITDA?
They are close cousins, not the same thing. Both strip out interest, taxes, depreciation, and amortization to show operating performance. NOI is the real estate version and goes one step further: it is calculated at the property level, it excludes corporate overhead, and it includes property taxes as an operating expense. EBITDA belongs to the operating company. NOI belongs to the building.
How do you check the NOI before you use it?
Three checks, in order, and they take about ten minutes.
Tie the totals to the source. Your annual gross rental income should match the number printed on the T12's total column, to the dollar. If it does not, the converter picked up a repeated header, dropped a row, or something is still stored as text. Do not adjust the model until that reconciles.
Reconcile the T12 against the rent roll. Annualize in-place rent from the converted rent roll and compare it to T12 gross rental income. They will not match exactly, and they should not: concessions, bad debt, and mid-year turnover all sit between them. A gap of a few percent is normal. A gap of fifteen percent means the rent roll is stale, the property is bleeding collections, or you are reading a different property. Where the leases themselves carry escalations and options that change the picture, someone still has to pull the key terms out of each lease before the rent roll can be trusted as forward-looking.
Verify collections against the bank. An operating statement is prepared by the seller. Deposits are not. If the package includes the property's bank records, comparing actual deposits to reported collections is the single strongest tell that the income line is real.
What is a good NOI?
There is no absolute number, because NOI scales with the size of the property. A hundred unit building should produce far more of it than a fourplex. What matters is NOI relative to price, which is the cap rate, and NOI relative to debt, which is the debt service coverage ratio. Divide NOI by purchase price for the cap rate. Divide NOI by annual debt service for DSCR, where most lenders want at least 1.25.
What makes an NOI good in the sense you actually care about is that it is defensible. It came off the seller's own statement, the expenses were normalized rather than accepted, capital items were moved out of repairs, a market management fee was charged, and every line traces back to a page you can point to.
The short version
Convert the T12 out of the PDF so the figures are real numbers in real columns. Build effective gross income as rental income plus other income less vacancy. Sum operating expenses, with capital items, debt service, and depreciation left out and a market management fee left in. Subtract. Then reconcile the result against the rent roll and, if you can, the bank statements, before it goes anywhere near a valuation.
Most of the risk in that sequence is at the beginning, in the retyping. If you are working from property PDFs regularly, the real estate document converter handles rent rolls, T12s, and closing statements in the same pass, and the PDF to Excel converter covers everything else in the package.