Cap Rate Explained: How the Real-Estate Yield Ratio Actually Works

What cap rate actually measures

The capitalization rate — almost always shortened to cap rate — is the unlevered annual yield on a piece of income-producing real estate. It strips a property down to its rawest economic question: if you bought the building with cash, what return would it pay you in year one before any mortgage, before any capital improvements, before any tax shielding from depreciation? That number, expressed as a percentage of the purchase price, is the cap rate. The cap rate calculator on this site computes it from four inputs: property value, gross annual rent, expected vacancy, and annual operating expenses.

Cap rate sits at the centre of the way the entire commercial real-estate market is priced. Appraisers use it to value income property by inverting the formula. Brokers quote it in listings as the headline yield. Lenders use it to size loans against stabilised net operating income. Buyers and sellers argue about the right cap rate for a deal in exactly the way bond traders argue about the right yield for a bond. Knowing how the number is built — and what it deliberately leaves out — is the single biggest unlock for reading a rental property offering memorandum the way a professional reads it.

The metric is not a verdict. A 4% cap rate on a stabilised prime multifamily asset in central London is unremarkable; a 4% cap rate on a tertiary-market strip mall is alarming. The rest of this guide is about how to read cap rates with the context that turns them from a number into a signal.

The formula behind the number

Cap rate is a two-step calculation. First you build net operating income (NOI) from the income statement of the property; then you divide it by the price someone is paying or asking. The arithmetic is elementary, the definitions are where the discipline lives.

Effective Gross Income (EGI) = Gross Annual Rent × (1 − Vacancy Rate)
Net Operating Income (NOI)   = EGI − Operating Expenses
Cap Rate                     = NOI / Property Value × 100

Operating expenses include:
Property taxes, insurance, repairs, maintenance,
property management, owner-paid utilities, advertising,
HOA fees, landscaping, snow removal, on-site staff.

Operating expenses EXCLUDE:
Mortgage interest and principal, capital expenditures,
depreciation, income taxes, and the owner's salary.

The exclusions are the load-bearing part of the definition. Mortgage payments are left out because cap rate is unlevered by construction — including them would conflate the property's yield with the buyer's specific financing choices. Capital expenditures are left out because they are lumpy and non-recurring; bundling a roof replacement into annual NOI would crash the cap rate for one year and artificially flatter it for the next twenty. Depreciation is an accounting fiction in this context — it never represents cash leaving the building. Income taxes vary by the owner's personal circumstances, not the property's. Strip all four out and you are left with the property's standalone earning power.

Worked example: a $500,000 duplex

Take a duplex listed at $500,000 in a suburban market. Both units rent for $2,000 a month, giving gross annual rent of $48,000. Local market data suggests a 5% vacancy assumption is reasonable. Annual operating expenses come in at $12,000 — property tax $5,500, insurance $1,800, repairs and maintenance reserve $2,400, property management at 6% of collected rent ($2,300). The arithmetic flows straight into the formula.

Effective Gross Income = $48,000 × (1 − 0.05) = $45,600
Net Operating Income   = $45,600 − $12,000    = $33,600
Cap Rate               = $33,600 / $500,000   = 6.72%
Gross Rent Multiplier  = $500,000 / $48,000   = 10.4x
Implied Value at 7%    = $33,600 / 0.07       = $480,000

Six-and-three-quarters per cent unlevered yield. For a suburban duplex in 2026, that lands at the lower edge of the market range — a buyer demanding a market-clearing 7% cap rate would only pay about $480,000 for the same NOI, so the $500,000 asking price embeds a roughly 4% premium to the market yield. That premium might be defensible (rising rents, improving submarket, low cap-ex backlog) or it might not. The number itself does not decide; it frames the conversation. Run the same example in the cap rate calculator and adjust the vacancy assumption to 7% or the expenses to $14,000 — the cap rate drops to about 5.7%, which would be outside the buyer's acceptable range altogether.

The same property analysed with a mortgage looks completely different on a levered basis. Put 25% down at $125,000, take a $375,000 loan at 6.5% over thirty years (monthly payment about $2,370), and the cash-on-cash return on the $125,000 of equity is roughly 4.1% — meaningfully below the 6.72% cap rate. That is negative leverage in action: the mortgage rate is above the property yield, so the borrower earns less return per dollar of equity than the unlevered cap rate suggested. The mortgage repayment calculator will work the loan payment, and the ROI calculator will work the levered annualised return.

What moves cap rates

Interest rates and the risk-free return

Real estate is one option among many for capital. When ten-year treasury yields move from 1.5% to 4.5%, the yield required on a risky illiquid asset like commercial real estate has to move too — typically by less than the treasury move, but in the same direction. The 2022–2024 rate cycle pushed cap rates 100–200 basis points wider across most US commercial sectors, and prices fell accordingly. The relationship is not instantaneous and gets disrupted by capital flow trends (foreign demand, allocation shifts from institutional investors), but the long-run direction is consistent over rate cycles.

Asset class and tenant quality

Industrial warehouses leased to investment-grade tenants on ten-year triple-net leases trade at the tightest cap rates because the cash flow is bond-like. Single-tenant retail properties with credit tenants are similar. Multifamily sits in the middle — short leases but resilient demand. Office and regional malls trade wider because tenant quality, lease rollover risk, and structural headwinds are worse. The cap rate captures all of that risk in a single number.

Location and market depth

A six-storey apartment building in Manhattan, Mayfair, or central Sydney trades at a much lower cap rate than the same building in a tertiary US Sunbelt market. Capital chases liquidity and growth, both of which compress cap rates. The compensation for accepting an illiquid secondary-market deal is the wider cap rate — the question for any investor is whether the spread is enough for the genuine risks involved.

Lease structure and expense responsibility

A triple-net (NNN) lease, where the tenant pays property taxes, insurance, and most maintenance, produces a higher NOI margin and a more bond-like cash flow than a gross lease where the landlord pays everything. Two superficially similar buildings can show very different cap rates simply because of the lease structure. Always check what the tenant is responsible for before comparing cap rates between deals.

The capex backlog

A building with a fresh roof, new HVAC, and recently turned units has a low capex backlog and a stable NOI. The same building five years later, with all of those systems near end-of-life, has the same headline cap rate but a hidden capex cliff. Sophisticated buyers underwrite a capex reserve (often 5–10% of gross rent for residential, more for older buildings) into operating expenses to surface this. The published cap rate then drops to a more honest stabilised figure.

How to use cap rate well

• Always compare to direct comparable sales. A 6% cap rate means nothing in isolation; it means everything compared to the 5.5% cap rates achieved on three similar buildings sold in the same submarket in the last six months. Co-Star, RCA, and the regional broker quarterly reports publish recent transaction cap rates by market and asset class — use them.
• Normalise the NOI before comparing. Re-build NOI on your own assumptions for vacancy, management fee, and reserves before computing the cap rate. Offering memoranda routinely present pro-forma NOI with optimistic vacancy and zero management fee; a re-underwritten "actual" cap rate is usually 50–150 basis points wider than the marketed figure.
• Pair the cap rate with the IRR. Cap rate measures year-one yield; it says nothing about rent growth, exit cap rate, or the value-add plan. The internal rate of return calculator and the NPV calculator let you model a multi-year hold and surface the difference between a low-going-in cap rate with strong growth (often a winning trade) and a high-going-in cap rate with declining rents (often a value trap).
• Stress-test the inputs. Rerun the cap rate at 10% vacancy instead of 5%, with expenses 20% higher than the offered figure, and at a 50 basis point higher exit cap rate. If the deal still works in that scenario, it is genuinely defensive. If it does not, the margin of safety is thinner than the headline number suggests.
• Watch the spread to debt cost. When the cap rate is at or below the mortgage interest rate, you are in negative leverage territory — the borrower earns less per dollar of equity than the unlevered yield. That is sometimes acceptable on a value-add deal where the plan is to push rents and re-lever later, but it is usually a red flag on a stabilised acquisition.
• Track market cap rates over time. A single deal evaluated in isolation tells you nothing about where the market is heading. Plot transaction cap rates by asset class over five years and you will see the cycles that drive every multi-year real-estate decision.

Common mistakes

Mixing pro-forma and actual NOI. Offering memoranda usually present a stabilised pro-forma NOI built on optimistic assumptions. Computing the cap rate from pro-forma NOI and comparing it to trailing actual cap rates achieved in real transactions is comparing apples to apples — except the apples have been polished. Always build your own actual NOI before computing the cap rate you use to compare against the market.

Including mortgage payments in operating expenses. Beginner spreadsheets routinely fold the mortgage payment into expenses and call the result "the cap rate". The resulting number is not a cap rate at all — it is a levered residual yield specific to that buyer's financing. Cross-buyer comparison falls apart immediately.

Ignoring vacancy entirely. Using gross rent in the numerator instead of effective gross income flatters the cap rate by 3–8% depending on the assumption. Every market has structural vacancy; a 0% vacancy assumption is never realistic and never the basis for a defensible underwriting.

Comparing cap rates across asset classes. A 5% cap rate on a Class A multifamily building is not comparable to a 5% cap rate on a suburban office building or a single-tenant net-lease pharmacy. Different asset classes have completely different risk profiles, and the cap rate already prices them differently. Always compare like with like.

Treating cap rate as a return. Cap rate is a yield, not a total return. It captures year-one income but ignores future rent growth, depreciation tax shield, mortgage amortisation, and exit value. For a real total return, forecast cash flows, build a sale year, and run the IRR calculator on the levered cash flow stream.

When to bring in a professional

For a single rental house, the cap rate calculator and a few comparable sales from a local broker are usually enough. For a multifamily building over five units, a small office property, or anything where the going-in price exceeds $1 million, the right move is to engage an independent appraiser or a commercial broker who routinely closes deals in the submarket. They will pull recent comparable sales, normalise the NOI on standard market assumptions, and produce a cap-rate-based valuation alongside a sales-comparison and a cost-approach figure. For regulated-product structures — a real estate fund, a crowdfunded syndication, or an institutional joint venture — bring in legal and tax advisers familiar with the relevant jurisdiction before signing anything. Cap rate is a useful tool; it is not a substitute for diligence on a major capital commitment.

Frequently asked questions

What counts as a "good" cap rate? It depends on the asset class, location, and prevailing risk-free rate. Prime urban multifamily trades at 4–6%; suburban and secondary markets at 6–8%; older single-family rentals at 8–10%+. Higher cap rates mean higher yield but higher risk or weaker appreciation. Always benchmark against direct comparable sales rather than national rules of thumb.

What is the difference between cap rate and ROI? Cap rate is unlevered (no mortgage); ROI is levered (after debt service, divided by cash invested). When cap rate exceeds mortgage interest rate, leverage amplifies returns and ROI exceeds the cap rate. When mortgage rates exceed cap rates, leverage shrinks returns and ROI lands below the cap rate.

Why are mortgage payments excluded from NOI? Cap rate is unlevered by definition. Including financing would conflate the property's yield with the buyer's specific loan structure and make cap rates non-comparable across buyers.

How does cap rate move when interest rates rise? Inversely most of the time. The 2022–2024 cycle expanded cap rates by 100–200 basis points across most US commercial sectors as treasury yields rose, and property values fell accordingly.

What is the gross rent multiplier (GRM)? GRM = Property Value / Gross Annual Rent. A simple screening ratio that ignores vacancy and operating expenses. Use GRM to filter listings; use cap rate to underwrite the shortlist seriously.

How do I use cap rate to estimate property value? Direct capitalisation: Value = Stabilised NOI / Market Cap Rate. A property netting $40,000 in a 6% cap submarket implies a value of about $666,667. The cap rate calculator shows the implied value at 7% as a built-in sanity check.

Related calculators

Pair the cap rate calculator with the ROI calculator to see the levered return on the same deal, the mortgage repayment calculator to size the loan, the rent vs buy calculator for the homeowner version of the same question, the buy-to-let mortgage calculator for UK rental investors, and the IRR calculator for multi-year hold analysis. Together they cover the analysis a careful real-estate investor runs on every prospective deal.