How to Calculate Cap Rate on a Rental Property

How to Calculate Cap Rate on a Rental Property

To calculate cap rate on a rental property, divide the property's net operating income (NOI) by its purchase price or current market value, then express the result as a percentage. The formula is: Cap Rate = NOI ÷ Property Value. A duplex generating $18,000 of NOI at a $250,000 price has a cap rate of 7.2%.

That is the whole equation. But the number is only as trustworthy as the NOI you feed it — and that is where most investors get it wrong. Below is exactly how to build a defensible cap rate, what counts as "good," and the traps that quietly inflate it.

The Cap Rate Formula, Step by Step

Cap rate measures the unlevered return of a property — the yield you'd earn if you paid all cash. Because it ignores financing, it lets you compare two properties on an apples-to-apples basis regardless of how each buyer funds the deal.

Work through it in this order:

1. Add up gross annual income

Start with realistic market rent, not the seller's pro forma. For a fourplex renting at $1,100 per unit:

• $1,100 × 4 units × 12 months = $52,800 gross scheduled rent

Add any real ancillary income — laundry, parking, storage — only if it actually exists.

2. Subtract vacancy and credit loss

No property stays 100% occupied. A 5–8% vacancy allowance is common in stable markets.

• $52,800 × 5% = $2,640 vacancy loss
• Effective gross income = $50,160

3. Subtract operating expenses

Operating expenses include everything needed to run the property — but not your mortgage, and not capital improvements like a new roof. Typical line items:

• Property taxes
• Insurance
• Property management (usually 8–10% of collected rent)
• Repairs and maintenance
• Utilities you pay
• Reserves for turnover and CapEx
• HOA fees, if any

Say those total $20,160 for the year. Then:

• NOI = $50,160 − $20,160 = $30,000

4. Divide NOI by value

If the asking price is $400,000:

• Cap Rate = $30,000 ÷ $400,000 = 7.5%

That is the number you compare against other deals and against the market.

What Counts as a Good Cap Rate?

There is no universal "good" cap rate — it is set by the market, the asset class, and the risk. A few honest guideposts:

• Lower cap rate (4–5%) usually signals a lower-risk, higher-demand area with strong appreciation potential and buyers willing to accept less current yield.
• Higher cap rate (8%+) often reflects more risk: softer tenant demand, older buildings, or markets with slower price growth.
• A cap rate that looks too high for the neighborhood is a red flag, not a bargain — it usually means the NOI is overstated or the area carries hidden risk.

The goal is not the highest number. It is the number that fairly prices the risk you're taking on.

Cap Rate vs. the Return You Actually Pocket

Cap rate ignores your loan, so it is not your take-home return. Two other metrics finish the picture:

• Cash-on-cash return factors in your mortgage and down payment — it tells you what your invested cash actually earns.
• Debt service coverage ratio (DSCR) tells the lender whether the NOI covers the loan payment. If you're financing the deal, review what lenders want on debt service coverage before you fall in love with a cap rate.

Use cap rate to price the asset. Use cash-on-cash and DSCR to size the financing. They answer different questions.

The Mistakes That Inflate a Cap Rate

Almost every bad cap rate traces back to a soft NOI. Watch for these:

1. Using seller pro forma rent. Sellers quote "market" rent that assumes rehab, perfect tenants, and zero vacancy. Verify rent against real comps.
2. Skipping reserves. Leaving out CapEx and maintenance can make a 6% deal look like an 8% deal. Roofs, HVAC, and turnover are not optional — they're deferred.
3. Understating taxes. In many areas property taxes reset to the new purchase price after a sale. Underwriting last year's tax bill overstates NOI on day one.
4. Confusing price with value. Cap rate on the asking price and cap rate on the appraised value can differ. Be clear which you're using.
5. Bad comps. If your rent and value assumptions rest on cherry-picked sales, the whole calculation is fiction. Learn to choose comps that won't lie to you.

Where Cap Rate Fits — and Where It Doesn't

Cap rate shines for stabilized, income-producing rentals, especially small multifamily where NOI is the primary value driver. It is far less useful for:

• Single-family flips, where you care about after-repair value and holding costs, not annual yield.
• Heavy value-add deals, where today's NOI is depressed and the whole thesis is future income.
• Appreciation-driven markets, where a low cap rate can still be a strong long-term hold.

Treat cap rate as one gauge on the dashboard, alongside total-return thinking that ties cap rate into your broader ratios, not a single go/no-go trigger.

Getting the Inputs Right Without the Guesswork

The formula takes ten seconds. Gathering trustworthy taxes, insurance, market rent, vacancy, and reserves for every property you screen is what actually eats your evenings — and a single soft assumption can swing the cap rate by a full point.

This is where analyzing deals with real, verified data beats typing guesses into a spreadsheet. Platforms like PropertyWiz AI pull live market data and pre-populate rent, taxes, insurance, vacancy, and more the moment you load a property, then stress-test the deal in real time — so your cap rate reflects the market instead of hopeful math.

Run the numbers honestly, price the risk fairly, and let cap rate do the one job it's good at: telling you what a property's income is worth today.