What Is a Cap Rate? A Beginner’s Guide to Real Estate Math
If you’ve spent more than five minutes looking into real estate investing, you’ve run into the term “cap rate.” It gets thrown around constantly — by investors, brokers, and YouTube gurus alike — and almost nobody explains it in plain English.
So let’s fix that.
A cap rate, short for capitalization rate, is simply a way to measure how much income a property produces relative to its price. It’s the single most commonly used metric in commercial real estate, and once you understand it, you’ll use it every time you look at a deal.
The Cap Rate Formula
Here’s all the math you need:
Cap Rate = Net Operating Income ÷ Property Value
That’s it. Two numbers divided by each other, expressed as a percentage.
Let’s make it concrete. Say you’re looking at a small retail strip center listed at $1,000,000. After collecting all the rents and paying all the operating expenses — property taxes, insurance, maintenance, management fees — the property produces $70,000 per year in net income. Plug those numbers in:
$70,000 ÷ $1,000,000 = 0.07, or a 7% cap rate.
That 7% is your cap rate. It tells you that if you paid all cash for this property, you’d earn a 7% return on your money from operations alone — before financing, before appreciation, before anything else.
What Is Net Operating Income (NOI)?
You’ll notice the formula uses “net operating income,” not just rent. This is an important distinction.
NOI is what’s left after you subtract operating expenses from gross rental income. Operating expenses include things like property taxes, insurance, utilities (if landlord-paid), property management fees, repairs, and maintenance.
What NOI does not include: mortgage payments, depreciation, or income taxes. Cap rate is a pre-financing, pre-tax metric. That’s intentional — it lets you compare properties on equal footing regardless of how they’re financed.
So if a property collects $120,000 in annual rent but has $50,000 in operating expenses, the NOI is $70,000. That’s the number you use.
What’s a Good Cap Rate?
This is where most beginners get confused, because the answer is: it depends entirely on the market and the property type.
As a general rule of thumb in today’s market:
- 4–5% cap rates are typical for trophy assets in major cities — think luxury apartment buildings in Manhattan or prime retail in downtown Chicago. Low cap rate means high price relative to income. Investors accept lower returns in exchange for perceived safety and appreciation potential.
- 6–7% cap rates are common for solid suburban commercial properties — well-leased retail centers, medical office buildings, industrial properties in secondary markets. This is where a lot of institutional money sits.
- 8–10%+ cap rates show up on riskier assets — older properties, weaker markets, short lease terms, less creditworthy tenants. Higher cap rate means more income relative to price, but usually for a reason.
I’ve bought properties at cap rates ranging from 6% to nearly 9%, and the cap rate alone never told me whether a deal was good. It’s a starting point, not a verdict.
Cap Rate and Property Value: Two Sides of the Same Coin
Here’s something that trips up a lot of beginners: cap rate and property value move in opposite directions.
When cap rates go up, values go down. When cap rates compress (go lower), values go up.
Why? Because the formula works both ways. If a property produces $70,000 in NOI and the market cap rate is 7%, the property is worth $1,000,000 ($70,000 ÷ 0.07). But if market cap rates compress to 6% — meaning buyers are willing to accept a lower return — that same $70,000 in income is now worth $1,166,667 ($70,000 ÷ 0.06).
The income didn’t change. The property’s value went up by $166,000 simply because buyers became more aggressive. This is one of the primary ways commercial real estate investors build wealth — not just by increasing rents, but by buying at one cap rate and selling when the market has compressed.
What Cap Rate Doesn’t Tell You
Cap rate is a useful tool, but it has real limitations. Here’s what it won’t tell you:
It ignores financing. A 7% cap rate property financed at 7% interest produces very different cash flow than the same property financed at 4%. Cap rate doesn’t care about your mortgage.
It’s only as good as the income numbers. If a seller gives you inflated rents or understated expenses, your cap rate calculation is worthless. Always verify NOI independently — get actual leases, actual tax bills, actual insurance invoices.
It doesn’t account for future changes. A property with a 7% cap rate today could drop to 5% if a major tenant leaves. Cap rate is a snapshot, not a forecast.
It’s not designed for single-family homes. Most residential investors use different metrics — price-to-rent ratio, gross rent multiplier — because cap rates on houses are often so low they’re not meaningful.
How to Use Cap Rate in Practice
When I’m evaluating a commercial property, cap rate is the first number I calculate — but it’s rarely the last thing I look at.
Start with the seller’s stated NOI and calculate the implied cap rate. Then ask yourself: does this cap rate make sense for this market and this property type? If a seller is claiming a 9% cap rate on a well-leased property in a strong market, something is off — either the numbers are wrong, or there’s a problem with the property they’re not advertising.
Next, calculate what the property would be worth at a more realistic cap rate. This gives you a sense of whether you’re overpaying, underpaying, or right at market.
Finally, stress-test it. What does the cap rate look like if vacancy goes up 10%? What if a tenant leaves and you lose 20% of your income? If the deal only works at the seller’s exact projections, it’s not a deal — it’s a bet.
A Quick Example to Tie It Together
Let’s say you’re looking at a small office building with four tenants. The asking price is $800,000. The seller claims $60,000 in annual NOI.
$60,000 ÷ $800,000 = 7.5% cap rate.
You do your homework and discover that one tenant’s lease expires in eight months, representing $18,000 of that annual income. Adjusted NOI if that tenant leaves: $42,000.
$42,000 ÷ $800,000 = 5.25% cap rate.
Suddenly that “7.5% cap rate deal” looks a lot less interesting. This is exactly why you verify the numbers yourself.
The Bottom Line
Cap rate is one of the most useful and most misused numbers in real estate. At its core it’s simple: income divided by price. But understanding how to use it — and more importantly, how not to be fooled by it — is what separates investors who make good decisions from those who overpay for bad deals.
Learn this number. Get comfortable with it. It will serve you for as long as you’re investing in real estate.
Mark Caldwell is a commercial real estate investor based in the Midwest with a portfolio spanning retail, industrial, and commercial properties across multiple states. PlainMoneyAdvice.com is where he writes about money the way he wishes someone had explained it to him.
