Net Operating Income Calculator

What the building earns, before the bank

Net operating income is what a property produces after the cost of running it and before the cost of financing it.

Rent in, operating expenses out, and stop. No mortgage payment, no interest, no tax on the profit.

That exclusion is what makes NOI useful rather than incomplete. Two people can buy the identical building on the same day, one with cash and one with 80 percent borrowed, and the building will produce exactly the same income for both. The difference in what reaches their pockets is a fact about them, not about the property.

So NOI describes the asset. It is what a valuation is built on, what a lender sizes a loan against, and the number every commercial property listing quotes. Give this tool the income, the expenses and a value, and it also returns the two ratios that come from it.

Nine fields and two units

Watch the units, because they change halfway down the form.

Income, entered monthly:

1. Rent Income per month.
2. Other Income per month. Parking, storage, laundry, pet fees, anything the property generates alongside rent.

Expenses, entered annually:

1. Real Estate Taxes per year.
2. Insurance per year.
3. Utilities per year, meaning whatever you pay rather than the tenant.
4. Maintenance per year.
5. Property Management per year.
6. Other Expenses per year.

Property Value is optional. Leave it blank and you get the NOI. Fill it in and you also get the cap rate and the gross rent multiplier.

The tool multiplies the two income figures by twelve and leaves the expenses as entered. So a monthly insurance premium typed into the insurance box will be counted as an annual figure and will understate your costs by a factor of twelve. Convert before you type.

The mortgage is not in here, and that is the point

There is no field for a mortgage payment, and people assume it is missing. It is deliberate, and it produces the most important thing to understand about this number.

Take the worked example below. The property produces an NOI of 16,056 a year.

Now suppose the owner has a mortgage costing 1,650 a month, which is 19,800 a year.

Cash flow after debt service: 16,056 minus 19,800 = minus 3,744.

The property earns sixteen thousand and the owner is out of pocket by nearly four. Both numbers are true and they answer different questions.

NOI says the asset is productive. Cash flow says this particular purchase, at this particular price, with this particular loan, does not pay for itself yet.

Which is exactly why lenders and valuers use NOI. It lets them assess the building without reference to whatever financing the current owner happens to have arranged. And it is why a buyer must never stop at NOI: a strong NOI with a mortgage that swallows it is a property you subsidise every month.

Work out both. The mortgage calculator gives you the annual debt service, and the difference between that and this figure is what actually reaches you.

A flat at 2,500 a month

Rent 2,500 a month, other income 150 a month. Annual expenses: taxes 4,800, insurance 1,800, utilities 2,400, maintenance 3,000, management 2,544, other 1,200. Property value 420,000.

Expenses are running at 49.5 percent of gross income, which is not unusual for a residential rental where the owner pays utilities and uses a manager. Investors often carry a rough expectation of somewhere around half, and it varies enormously with who pays what.

The cap rate of 3.82 percent is the number to focus on, and it is the subject of the next section, because it is not a return.

Cap rate is a price, read backwards

Cap rate = NOI ÷ property value × 100

People treat it as a yield on their investment. It is closer to a price tag, and the clearest way to see that is to hold the NOI still and move the value.

The building has not changed. Only what you pay for it. A lower cap rate means a more expensive property relative to what it earns.

Which makes the ratio far more useful inverted. If you know what cap rate the local market trades at, you can work out what a property should be worth:

Value = NOI ÷ cap rate

So a flat asking 420,000 in a market where comparable properties trade at a 5 percent cap looks expensive by roughly a hundred thousand.

There is a further consequence worth carrying. Because value is NOI divided by cap rate, every unit of NOI you add is worth many units of value. At a 5 percent cap, raising the NOI by 1,000 a year raises the property's worth by 20,000. That is the arithmetic behind putting rents to market, adding a parking charge, or cutting a management fee, and it explains why commercial investors chase small operating improvements so hard.

Low cap rates generally signal expensive markets, strong locations and lower perceived risk. High cap rates signal cheaper entry, weaker locations or more risk. Neither is good or bad on its own, and the comparison only means anything within one market and one property type.

The empty months nobody entered

There is no vacancy field, so the tool assumes the property is let for all twelve months at the full rent, every year, with every tenant paying.

That never happens. Tenants leave, units sit empty between lettings, and occasionally somebody does not pay.

Here is what allowing for it does:

An 8 percent allowance, which is roughly one empty month a year, costs 2,544 of NOI and takes 0.6 of a percentage point off the cap rate.

Notice that vacancy hits NOI harder than it hits income. The income fell by 8 percent and the NOI fell by 16 percent, because your expenses carry on regardless. Taxes, insurance and the mortgage do not pause when a flat is empty.

The fix is straightforward. Reduce the rent figure you enter by your expected vacancy before you type it. On 2,500 a month with an 8 percent allowance, enter 2,300. What you get back is then a realistic NOI rather than a best case.

And when you are assessing somebody else's numbers, this is the first thing to check. A seller quoting NOI at full occupancy is quoting the ceiling.

The roof that is not in your expenses

The six expense fields cover the recurring cost of running a property. They do not cover the occasional cost of replacing large parts of it.

The distinction matters for tax as well as for arithmetic. Under IRS guidance for residential rental property, a repair keeps the property in ordinary operating condition and is deducted in the year you pay it. An improvement adds value or extends the property's life, and it has to be capitalised and depreciated rather than expensed.

Fixing a leaking tap is maintenance and belongs in the maintenance box. A new roof is an improvement and does not.

Which leaves a gap in your planning, because the roof still needs paying for. Roofs, boilers, windows, kitchens and bathrooms all wear out on schedules of ten to thirty years, and none of them appears in an NOI calculation.

Investors handle this with a reserve. Estimate the replacement cost, divide by the expected life, and set that aside annually. A 12,000 roof on a twenty year life is 600 a year.

That reserve is not an operating expense and it should not go in the boxes, because NOI has a standard definition and adding to it makes your figure incomparable with everyone else's. But subtract it afterwards, before you decide whether the property works. On our example, 16,056 of NOI with a modest 600 reserve is really 15,456 of usable income, and a full set of reserves on an older building will take considerably more.

The gross rent multiplier, and what it is for

The third output is the gross rent multiplier.

GRM = property value ÷ gross annual income

On our flat that is 420,000 divided by 31,800, giving 13.21. Read it as the number of years of gross rent the purchase price represents.

It is a cruder measure than the cap rate, and that is its purpose. GRM ignores expenses entirely, which means you can calculate it for any property you can find an asking price and a rent for. You do not need the seller's accounts.

So it is a screening tool. Run it across a dozen listings, see which ones sit well outside the local pattern, and look harder at those.

What it cannot do is compare properties with different cost structures. A building where the tenant pays all utilities and one where the landlord pays them can show the same GRM and completely different NOI. A low GRM on a property with terrible expenses is a bargain that is not.

Use GRM to shortlist. Use cap rate, built on a realistic NOI, to decide.

This is a measurement of figures you supply rather than a valuation or an assessment of a property, and nothing here is investment or tax advice.

Questions people ask

How is net operating income calculated?

Total annual income from the property, less annual operating expenses. Financing costs and income tax are excluded by definition.

Why is my mortgage not included?

Because NOI measures what the property earns, not what the current owner's financing costs. A building produces the same NOI whether it was bought with cash or with a loan. Subtract your annual debt service separately to get your actual cash flow.

Are the income and expense fields on the same basis?

No. Income is entered monthly and expenses annually. The tool multiplies the income by twelve, so a monthly figure typed into an expense box understates that cost twelvefold.

Should I allow for empty periods?

Yes, and there is no field for it, so reduce the rent you enter. On 2,500 a month with an 8 percent vacancy allowance, enter 2,300. Vacancy hits NOI harder than income, because expenses continue when a unit is empty.

What is a good cap rate?

It reflects the market rather than the property's quality. Lower cap rates mean more expensive markets and lower perceived risk, higher ones mean cheaper entry or more risk. Only compare within one market and property type.

How do I use cap rate to value a property?

Divide the NOI by the market cap rate. An NOI of 16,056 in a market pricing at 5 percent implies a value of about 321,000.

Where do major repairs go?

Not in the expense boxes. A repair that keeps the property in operating condition is a maintenance expense, while an improvement that adds value or extends life is capitalised and depreciated. Set a reserve aside separately and subtract it after the NOI.

What is the gross rent multiplier for?

Quick screening. It needs only a price and a rent, so you can calculate it from a listing. It ignores expenses entirely, which makes it useless for a final comparison between properties with different cost structures.

References

The treatment of rental income, the list of deductible operating expenses including taxes, insurance, utilities, maintenance and management fees, and the distinction between a repair that keeps the property in ordinary operating condition and an improvement that must be capitalised and depreciated, follow Internal Revenue Service Publication 527 for residential rental property. The general treatment of ordinary and necessary business expenses follows IRS Publication 334. Net operating income excludes financing costs by definition, consistent with the separation of operating results from interest and income tax expense required in the income statements of registrants under Regulation S-X.

1. Internal Revenue Service, Publication 527: Residential Rental Property (Including Rental of Vacation Homes). https://www.irs.gov/publications/p527
2. Internal Revenue Service, Topic No. 414, Rental Income and Expenses. https://www.irs.gov/taxtopics/tc414
3. Internal Revenue Service, Publication 334: Tax Guide for Small Business. https://www.irs.gov/publications/p334
4. United States Securities and Exchange Commission, Regulation S-X, Rule 5-03: Statements of Comprehensive Income (17 CFR 210.5-03). Text quoted in SEC staff correspondence at https://www.sec.gov/Archives/edgar/data/0001019361/000101936112000010/filename1.txt