How to Calculate The Cap Rate | Formula That Holds Up

Cap rate equals annual net operating income divided by the property’s current value or purchase price, shown as a percentage.

Cap rate is one of the fastest ways to judge an income property. It tells you how much net operating income a property throws off compared with what you pay for it. That makes it handy when you’re comparing two rentals, checking an asking price, or stress-testing a deal before you sink more time into it.

The catch is simple: the math is easy, but the inputs trip people up. A cap rate built on rosy rent, skipped repairs, or the wrong purchase price can send you in the wrong direction. Get the inputs right, and the number becomes useful. Get them wrong, and it turns into decoration.

This article walks through the formula, shows the right way to build net operating income, and points out the mistakes that wreck the result.

What Cap Rate Tells You

Cap rate measures a property’s income return before debt. In plain English, it shows how much a property earns on its own, without mixing in your loan terms, down payment, or tax situation. That makes it a clean comparison tool.

A lower cap rate often shows a pricier asset with steadier income. A higher cap rate can point to more risk, weaker demand, more management drag, or a property that needs work. It does not tell you which deal is better by itself. It tells you where to ask the next question.

• Use cap rate to compare similar properties in the same market.
• Use it to sense-check an asking price against the income stream.
• Use it with other metrics, not as a stand-alone verdict.

How to Calculate The Cap Rate In 4 Steps

The formula is short:

Cap Rate = Net Operating Income ÷ Property Value

Then multiply by 100 to turn it into a percentage.

1. Start with gross annual rental income. Use rent you can defend, not the rent you wish the place could get.
2. Subtract vacancy and collection loss. Every market has friction. Leaving it out makes the deal look prettier than it is.
3. Subtract operating expenses. Think taxes, insurance, repairs, maintenance, management, utilities you pay, HOA dues, and routine admin costs.
4. Divide NOI by value or purchase price. Use current market value for market-based comparisons. Use purchase price when sizing up a live deal.

Quick cap rate example

Say a duplex brings in $36,000 a year in rent. You budget 5% for vacancy, or $1,800. Operating expenses run $11,200 a year. That leaves net operating income of $23,000.

If the property costs $320,000, the math is:

$23,000 ÷ $320,000 = 0.0719

That gives you a cap rate of 7.19%.

What belongs in NOI and what stays out

This is where plenty of people get sloppy. Net operating income is property income after ordinary operating costs. It does not include mortgage principal or interest. It also does not include income taxes, depreciation, capital improvements, or one-off renovation budgets. The IRS breaks out rental income and rental expense treatment in Publication 527, which is a solid checkpoint when you’re sorting expenses.

Appraisers and lenders also separate the cap rate from financing. Freddie Mac’s appraisal guidance makes that same distinction when it talks about deriving capitalization rates from income and sales data rather than loan terms. You can read that in its capitalization rate development guidance.

Calculating cap rate for a rental property without bad inputs

The formula stays the same on every property. The hard part is using numbers that match the real world. A few checks keep the result honest.

Use stabilized income, not a lucky month

If a unit just got leased at a rent spike after sitting empty for three months, that fresh rent may not be the whole story. Use a realistic annual figure. If the building is partly vacant, ask what a normal year looks like once the property is leased and managed in a steady way.

Use normal operating expenses, not a best-case budget

Repairs do not disappear because the roof behaved last year. Management has a cost even if you self-manage. If utilities are owner-paid in your market, count them. If turnover is common, build that into maintenance and leasing costs.

Match the denominator to the question

If you’re comparing listings, purchase price is fine. If you’re comparing a property with recent local sales, current market value can make more sense. Mixing these two without noticing can skew your read.

Line Item	Include In NOI?	How To Treat It
Gross scheduled rent	Yes	Use annual rent at a defendable market level.
Vacancy and collection loss	Yes	Subtract a normal allowance based on the property and area.
Other income	Yes	Add parking, laundry, storage, or pet fees if they recur.
Property taxes	Yes	Use the current bill or a realistic reset after sale.
Insurance	Yes	Count hazard and liability coverage tied to operation.
Repairs and maintenance	Yes	Use a yearly average, not a single quiet month.
Property management	Yes	Count it even if you manage the place yourself.
Utilities paid by owner	Yes	Include water, trash, power, gas, or internet you cover.
Mortgage payment	No	Leave financing out of cap rate.
Capital improvements	No	Do not treat a new roof or full rehab as an operating cost.

Common mistakes that twist the number

A cap rate can look tidy while hiding bad assumptions. These are the errors that show up most often.

Mixing cash flow with NOI

Cash flow comes after debt service. NOI comes before it. Blend the two, and the result stops being a cap rate.

Using gross rent instead of collected income

Leases on paper do not pay the bills. Late payments, skipped months, and turnover matter. That gap belongs in your numbers.

Leaving out management

Self-managing is still work with a market cost. A buyer who needs third-party management will price that in, so your cap rate should too.

Forgetting taxes may reset

Property taxes can jump after a sale. If you use the seller’s old tax bill without checking local rules, your NOI may come out too high.

Treating cap rate like a full return metric

Cap rate is not your total return. It skips loan terms, future rent growth, sale timing, depreciation, and tax treatment. It’s a strong screening metric, not the whole verdict.

How to read a cap rate once you have it

The same cap rate can mean different things in different places. A 5% cap in a prime urban pocket may be normal. A 7% cap in a softer market may be normal too. What matters is the gap between this property and similar properties nearby, plus the reason behind that gap.

NAIOP’s commercial real estate terms note that an entry cap rate is the projected first-year NOI divided by acquisition price. That wording helps because it reminds you the ratio is tied to both the income assumption and the deal price. You can see that in NAIOP’s terms and definitions report.

• Lower than market: check whether the asset has stronger rent growth, lower risk, or just an inflated price.
• Near market: the deal may be priced in line with local expectations.
• Higher than market: ask what problem the buyer is being paid to take on.

Cap Rate Result	What It May Signal	Next Check
Below nearby comps	Higher price, steadier income, stronger location	Check rent growth, tenant strength, and downside risk.
In line with nearby comps	Pricing fits the local market	Review leases, deferred maintenance, and tax reset risk.
Above nearby comps	More risk, more work, or weaker demand	Find the reason before calling it a bargain.

When cap rate works well and when it falls short

Cap rate works best on stabilized income properties with a track record you can verify. Single-family rentals, small multifamily, retail pads, and larger commercial assets all use it, though the market context changes from one property type to the next.

It gets weaker when a property is in flux. A heavy rehab, a lease-up project, a building with big near-term capital needs, or a property with choppy seasonal income may need a wider set of tools. In those cases, cash-on-cash return, debt service coverage, and multi-year underwriting tell you more.

A simple way to sanity-check your answer

After you run the formula, flip it around and read it like a buyer. If the cap rate is 6%, the property produces about 6 cents of NOI for each dollar of value. Ask yourself whether that fits the location, condition, tenant mix, and rent level.

Then run the number again with slightly tougher assumptions. Trim rent a bit. Add a vacancy allowance if you skipped it. Raise repairs if the property is older. If the cap rate falls apart with small changes, the deal may be thinner than it first looked.

That’s the real use of cap rate. It gives you a sharp first read, then it pushes you toward better questions.