Cap Rate vs Cash-on-Cash Return: Which Number Should Drive the Offer?

Two properties, both listed at a 6% cap rate. One returns 9% on your cash. The other returns 1%. Nothing about the properties changed; the difference is in the financing, and cap rate cannot see financing.

That is the whole cap rate vs cash-on-cash argument in one paragraph. This post shows the math on a single property, explains when each metric is the right one, and answers the question that matters: which number should decide your offer?

Definitions, without the fog#

Cap rate (capitalization rate) is net operating income divided by purchase price.

Cap rate = NOI ÷ Price

NOI is rent minus operating expenses, before any mortgage payment. Cap rate describes what the property produces relative to what it costs, as if you paid cash. It is a property metric.

Cash-on-cash return is annual cash flow divided by the cash you actually invested.

Cash-on-cash = (NOI − Debt service) ÷ Cash invested

Cash flow is what is left after the mortgage. Cash invested is the down payment plus closing costs (plus rehab if you did any). Cash-on-cash describes what your money earns. It is an investor metric.

Cap rate answers: is this a productive asset at this price? Cash-on-cash answers: is this a good use of my $75,000?

The worked example#

Same property used across our deal analysis series, so the numbers carry over.

Now finance it at 20% down, 6.0%, 30 years.

• Loan: $260,000 → payment $1,559/month → $18,706/year
• Cash invested: $65,000 down + $9,750 closing = $74,750
• Cash flow: $19,370 − $18,706 = $664/year
• Cash-on-cash: 0.9%

A 5.96% cap rate became a 0.9% return. The listing sheet would call this a solid rental. Your bank statement would not.

Why they diverge: the mortgage constant#

The quiet number behind this is the mortgage constant: annual debt service divided by the loan amount. At 6% over 30 years it is $18,706 ÷ $260,000 = 7.2%.

When the mortgage constant is below the cap rate, borrowing helps. Each borrowed dollar earns the cap rate and costs the constant, so the spread accrues to your equity. That is positive leverage.

When the constant is above the cap rate, borrowing hurts. Each borrowed dollar costs more than it earns, and your cash absorbs the difference. That is where this property sits: 7.2% constant against a 5.96% cap rate. Leverage is working against the investor.

The practical rule: compare the cap rate to your mortgage constant before you compare it to anything else. If the constant is higher, more leverage means lower cash-on-cash, and no amount of "but it's a 6-cap" fixes that.

The same math when leverage helps#

To see the rule work in the other direction, take a cheaper property in a higher-cap market.

Cash flow is $15,000 − $10,902 = $4,098 on $46,000 invested: 8.9% cash-on-cash. Paid in cash, the same property would return 7.5% (the cap rate, less nothing). Borrowing raised the return by 1.4 points, because each borrowed dollar earned 7.5% and cost 6.8%.

Same formulas, opposite result. The first property's 5.96% cap rate lost to a 7.2% constant; this one's 7.5% cap rate beats a 6.8% constant. Cap rate alone would have ranked them 7.5% vs 5.96%, a modest edge. Cash-on-cash ranks them 8.9% vs 0.9%, a tenfold one. The financing did that, and only one of the two metrics can see it.

What changes each metric#

The middle rows are the ones that matter for an offer. Rate, down payment, and seller financing move cash-on-cash and leave cap rate untouched. A negotiation built on cap rate cannot use those levers.

What is a "good" number?#

Cap rate is market-relative. Newer single-family in a high-demand metro often trades at 4% to 5%. Secondary markets and older small multifamily run 6% to 8%. A higher cap rate is more income per dollar and usually more risk or slower appreciation. The national benchmarks page shows the typical ranges DealGapIQ uses as defaults.

Cash-on-cash is personal. Many investors underwrite to 6% to 10% on a conventional purchase, reasoning that anything below what a low-risk alternative pays is not worth the tenants. Your number depends on your alternatives, your appetite for appreciation risk, and whether you are counting loan paydown.

The mistake is using one where the other belongs. "This is a 6-cap market, so 6% is fine" is a cap rate answer to a cash-on-cash question.

Which number should drive the offer?#

Cash-on-cash, or a debt coverage threshold that amounts to the same thing.

Here is the reasoning. An offer is a price and a financing structure. Cap rate ignores the structure, so it cannot tell you what price the structure supports. Cash-on-cash includes the structure, so you can set the return you need and solve backward for price.

On the example property, solving for an 8% cash-on-cash return gives a Target Buy of $270,731. At that price: loan $216,585, payment $1,299, NOI $20,564, cash flow $4,981 on $62,268 invested, DSCR 1.32. The cap rate at that price would be 7.6%, but nobody decided anything with it. The cash-on-cash target produced the price; the cap rate is a by-product.

The distance from asking to Target Buy is the Deal Gap: here, 16.7%.

Where cap rate still earns its keep#

Cap rate is not useless. It is the right tool for three jobs.

Comparing properties to each other. Two listings at different prices with different rents are hard to compare on cash flow. Cap rate normalizes them.

Reading a market. If your target submarket trades at 5.5% and a listing pencils at 7%, either the rent is overstated, the expenses are understated, or something is wrong with the property. Cap rate is a smoke detector.

Valuing on exit. When you sell to another investor, they will price your NOI at the market cap rate. A $2,000/year NOI improvement at a 6% cap is worth about $33,000 of price. Cap rate is how operational improvements become equity.

The one-line version#

Cap rate tells you what the building earns. Cash-on-cash tells you what you earn. Offer on the second, compare on the first, and never let a listing's cap rate stand in for your return.

In DealGapIQ the Deal Maker shows both side by side as you change price, rate, down payment, and seller-financing terms, so you can watch the cap rate hold still while cash-on-cash moves.

We analyze. You decide. Not financial, legal, or investment advice. Figures are illustrative and use editable assumptions.