What cap rate is really measuring
Cap rate answers a specific, deliberately narrow question: if you bought this property in cash, with no mortgage at all, what percentage return would its income alone generate on your money each year? Because it removes financing entirely, a property's cap rate doesn't change based on whether you put 20% down or paid cash — it's a property-level metric, not a deal-structure-level one.
That narrowness is exactly what makes cap rate the standard way commercial and residential investors compare properties across different markets, price points, and financing situations on equal footing. It's not a complete investment thesis by itself — it says nothing about appreciation potential or neighborhood trajectory — but as a first-pass screening tool, it's hard to beat.
The formula, step by step
Step 1 — Effective gross income
EGI = Gross Rent × (1 − Vacancy %)
Step 2 — Net operating income
NOI = EGI − Operating Expenses
Operating expenses include property management, insurance, property tax, maintenance, HOA, and other recurring costs — but never mortgage principal or interest.
Step 3 — Cap rate
Cap Rate = (NOI ÷ Property Value) × 100
What actually moves your cap rate
- Vacancy assumption. Assuming full occupancy when real-world vacancy is 5-8% overstates NOI and cap rate together.
- Expense accuracy. Pro forma numbers from a listing often understate real insurance, tax, and maintenance costs.
- Property value used. Purchase price versus current appraised value can produce meaningfully different cap rates on the same property.
- Market cap rate compression. In competitive markets, rising prices can outpace rent growth, pushing cap rates down even for properties with unchanged income.
- Property age and condition. Older buildings typically carry higher maintenance costs, which lowers NOI relative to a comparably priced newer property.
Same price, same rent, different expenses
Both examples share a $500,000 property and $48,000 gross annual rent with 5% vacancy — only operating expenses differ.
Example A — well-maintained, modern building
Roughly $18,600 in annual operating expenses. NOI lands near $27,000, producing a cap rate of about 5.4%.
Example B — older building, higher maintenance and insurance
Same price and rent, but $26,000 in annual operating expenses due to age-related maintenance and higher insurance costs. NOI drops to around $19,600, and cap rate falls to roughly 3.9%.
Same price, same rent, meaningfully different return — which is exactly why expense accuracy matters as much as the rent figure. Run your own numbers with the Cap Rate Calculator.
Benefits of using cap rate to screen deals
✓ What you gain
- A financing-independent way to compare properties across markets
- A quick sanity check against a seller's advertised numbers
- A consistent benchmark for tracking a market's typical range over time
- A way to spot when a listing's pro forma looks inflated
- A shared vocabulary with other investors and lenders
✗ What cap rate doesn't tell you
- What your actual return will be once your specific mortgage is factored in
- Future appreciation or rent growth potential
- Neighborhood trajectory or development risk
- Capital expenditure needs coming due, like a roof or HVAC replacement
- How quickly a similar property would actually sell if you needed liquidity
Practical tips
Verify a seller's advertised cap rate independently
Pro forma income and understated expenses are a common way listings present an optimistic number. Rebuild the calculation yourself from realistic assumptions before trusting it.
Know your market's typical range before you compare
A cap rate that looks attractive in one market may be mediocre in another — always benchmark against comparable properties in the same specific area.
Never fold debt service into NOI
This is the single most common cap rate calculation error. NOI must stay capital-structure independent for the comparison to mean anything.
Pair cap rate with cash-on-cash return
Cap rate shows the property's unlevered strength; the Cash-on-Cash Return Calculator shows what your specific financing does to that return. Run both before deciding.
Don't treat a lower cap rate as automatically worse
Lower cap rates often reflect lower-risk, higher-demand, higher-appreciation-potential markets. The tradeoff can be entirely intentional, not a red flag by itself.
Calculate your cap rate
Get NOI and cap rate from your actual rent, vacancy, and expense numbers.
Bottom line
Cap rate is powerful precisely because of what it leaves out — financing, appreciation assumptions, your personal tax situation — which makes it a clean, comparable number across very different deals. Just remember what it isn't: a complete investment thesis, or a guarantee that a high number means a good deal. Use it to screen, verify the inputs independently, and pair it with the Cash-on-Cash Return Calculator before deciding. Get your own number with the Cap Rate Calculator.
Frequently Asked Questions
What is cap rate in real estate?
Cap rate, short for capitalization rate, measures a property's net operating income as a percentage of its current market value or purchase price, giving an unlevered measure of return independent of financing.
How do you calculate net operating income (NOI)?
NOI is calculated by subtracting operating expenses, such as property management, insurance, maintenance, taxes, and vacancy loss, from gross rental income, before accounting for mortgage payments or capital expenditures.
What is a good cap rate for a rental property?
Typical cap rates range from about 4 to 10 percent depending on market, property class, and risk profile. Lower cap rates often reflect lower-risk, higher-demand markets, while higher cap rates may reflect higher risk or lower-growth areas.
Does cap rate include mortgage payments?
No. Cap rate is calculated before financing costs, making it useful for comparing properties independent of how each is financed. For a return metric that includes a mortgage, cash-on-cash return is used instead.
Why does cap rate matter when comparing properties?
Because it strips out financing differences, cap rate lets investors compare the income-generating efficiency of different properties or markets on a like-for-like basis.
Can cap rate be negative?
Yes, if operating expenses and vacancy losses exceed gross rental income, NOI turns negative, producing a negative cap rate, which signals the property is losing money on operations alone before financing costs are considered.
How does cap rate change as property values rise or fall?
If NOI stays flat while property value rises, cap rate falls, and vice versa. This is why cap rate compression often accompanies a hot market, as rising prices outpace rent growth.
Is a higher cap rate always a better deal?
Not necessarily. A high cap rate can reflect genuine value, but it can also signal higher risk, a declining market, deferred maintenance, or a less desirable location.
What expenses are included in NOI but not in cash flow?
NOI includes all normal operating expenses but excludes mortgage principal and interest, and typically excludes capital expenditures like a roof replacement, which are treated separately from ongoing operations.
How is cap rate different from cash-on-cash return?
Cap rate measures return on the full property value independent of financing. Cash-on-cash return measures return specifically on the cash actually invested, factoring in the mortgage payment, so the two can differ significantly on a leveraged deal. See the Cash-on-Cash Return Calculator for that side of the comparison.
Should I trust a seller's advertised cap rate?
Verify it independently. Sellers sometimes use optimistic pro forma income and understated expenses to advertise a higher cap rate than the property would actually produce under realistic operating assumptions.
Does cap rate account for future rent growth?
No, a standard cap rate calculation uses current NOI and current value, treating the return as a snapshot rather than a forecast. Future rent growth is a separate consideration layered on top.
How do vacancy rates affect cap rate?
Higher vacancy reduces effective gross income, which lowers NOI and therefore cap rate. Using a realistic, market-appropriate vacancy assumption rather than assuming full occupancy is essential for an accurate figure.
Is cap rate useful for single-family rentals or just commercial property?
It's useful for both, though it originated in and is used more heavily in commercial real estate. Single-family investors increasingly use it alongside cash-on-cash return to compare deals on a like-for-like basis.
How do I calculate my own cap rate?
Use the free Cap Rate Calculator on CalcPro, which computes NOI from your gross rent, vacancy assumption, and operating expenses, then divides by property value to show your cap rate.