Cap Rate Explained: NOI, Value, and a Worked Example

The short version

Short answer: Cap rate is net operating income (NOI) divided by property value. NOI is the rent the property actually keeps after vacancy and operating expenses, with the mortgage left out on purpose. On the labeled hypothetical below, a $425,000 property with $20,342 of NOI runs at a 4.79 percent cap rate, and the same formula reversed (value = NOI / cap rate) is how income-producing property gets valued. Every dollar figure in this guide is a worked example, not market data, and none of it is financial advice.

If you have already worked through our rental yield guide, this is the companion calculation. Yield screens rent against price. Cap rate standardizes the expense treatment and adds the valuation direction, which is why agents, appraisers, and lenders reach for it when properties are bought mainly for income.

The formula and the two directions

The standard definition, as published in real estate investment references (see the sources at the end of this guide), is:

• Cap rate = NOI / current market value (or purchase price) x 100
• Value = NOI / cap rate

The first direction answers a return question: for each dollar of value, how much net operating income does this property produce in a year, before financing? The second direction answers a price question: if properties of this type in this market trade at a given cap rate, what is this income stream worth? Both directions use the same two inputs, and both stand or fall on whether the NOI is complete and verifiable.

A cap rate is a snapshot of one stabilized year. It assumes the income figure you feed it is repeatable. Feed it a best-ever year, a below-market lease about to expire, or expenses scrubbed for the sale brochure, and the percentage will look precise while describing a property that does not exist. The arithmetic is the easy part. The work is in the NOI.

Building NOI properly

NOI has three steps, and each step has a place where optimistic numbers sneak in.

Step 1: From scheduled rent to effective gross income

Start with gross potential rent: the rent if every unit were occupied at the agreed rate for the full year. Then subtract a vacancy and credit-loss allowance to reach effective gross income (EGI). Add any other real property income (parking, laundry, storage fees) only if it is actually collected under the current setup.

The vacancy line is not pessimism. It is the admission that units turn over, tenants occasionally pay late or not at all, and reletting takes weeks. A seller statement showing zero vacancy across several years is either an exceptional property or an incomplete statement. Ask which one, and check the lease history.

Step 2: Subtract operating expenses

Operating expenses are the recurring costs of keeping the property occupied and in repair:

• Property taxes
• Insurance
• Maintenance and routine repairs
• Property management fees, even if you currently self-manage and would rather not count your own time
• Landlord-paid utilities, landscaping, snow, and common-area costs
• Licensing, inspections, and accounting where they apply

Use the property's actual expense history where you can get it (a trailing twelve-month statement, often called a T12), and treat a seller's forward-looking pro forma as a claim to verify line by line. The commonest gap is management: an owner who self-manages may show no management cost, which flatters NOI for a buyer who will hire a manager. Restate that line at the market fee you will actually pay, and say that you did.

Step 3: Know what stays out, and why

NOI excludes:

• Mortgage payments and all debt service. The property earns the same income whoever owns it. Financing is a fact about the buyer, not the building, so it belongs in the cash-flow calculation, not here.
• Income tax and depreciation. Both depend on the owner's situation, not the property's operation.
• Major capital expenditures, such as a roof replacement or a new heating system. These are real costs, but they are lumpy capital, not annual operating costs. The way to account for them is a reserve line below NOI in your cash-flow work, sized from the building's actual age and condition. A pro forma with no reserve is cash flow until something breaks, presented as cash flow forever.

That third exclusion deserves emphasis. Leaving capex out of NOI is correct. Leaving it out of your thinking is how a good-looking cap rate turns into a bad year. Our closing costs guide covers the purchase-side costs that sit outside this formula entirely; budget for both lists, not one.

A worked example, fully labeled

Every figure in this section is hypothetical, chosen so you can rerun the arithmetic with your own numbers. It is not a price, rent, tax, or return figure for any real place.

The property (hypothetical): asking price $425,000. One rental home, market rent $2,750 per month.

Step 1: effective gross income. Gross potential rent = $2,750 x 12 = $33,000. Vacancy and credit-loss allowance at 5 percent = $1,650. Effective gross income = $33,000 - $1,650 = $31,350.

The 5 percent allowance is roughly two and a half weeks empty per year. Your market, property type, and tenancy history may justify more or less. State the assumption and test it, as the sensitivity table below does.

Step 2: operating expenses (all hypothetical).

Step 3: NOI and cap rate. NOI = $31,350 - $11,008 = $20,342. Cap rate = $20,342 / $425,000 x 100 = 4.79 percent.

Read that result narrowly and correctly: at the asking price, on these assumptions, the property produces net operating income equal to about 4.79 percent of its price per year, before any mortgage. It says nothing yet about your loan, your tax position, the roof's remaining life, or whether the $2,750 rent is actually achievable on that street. Those checks come next, and they are the purchase. The home buying guide sequences them from budget to keys.

The reverse direction: using cap rate to value

Rearrange the formula and cap rate becomes a pricing tool: value = NOI / cap rate. Using the same hypothetical NOI of $20,342:

Two lessons live in that table. First, small rate differences move value a lot: half a point of cap rate is worth tens of thousands of dollars on an ordinary rental, which is why buyers and sellers argue so hard over both the NOI and the rate. Second, the table prices the income, not the building. If the $20,342 NOI rests on a rent the street will not support, every implied value in the column is fiction at a different price. Verify the rent from current comparable lettings before you capitalize anything. Our affordability guide applies the same verify-the-input discipline to owner-occupier budgets, and the mortgage pre-approval guide covers the financing side that cap rate deliberately leaves out.

Where does the market cap rate in the left column come from in real life? From comparable income-property sales: divide each comparable's NOI by its sale price, then judge which comparables genuinely resemble your property in location, type, lease quality, and condition. That is appraisal work, and the rate you choose should be the one you can defend with named comparables, not the one that makes the answer come out where you wanted it.

What moves the number most

Precision in the division is worthless next to accuracy in the inputs. On the worked example:

• Vacancy is the largest single lever. Each additional empty month removes $2,750 of gross rent (about $2,613 after the allowance arithmetic), which is roughly 0.6 points of cap rate at this price. Pricing rent above what comparable homes achieve usually returns the apparent gain as vacancy.
• The management line is the quietest distortion. Deleting an 8 percent management fee because the current owner self-manages adds $2,508 to NOI in this example, about 0.59 points of cap rate, without changing the property at all. If you will hire a manager, the fee is a real cost of your ownership whatever the seller's statement says.
• A major repair does not move cap rate, and that is the trap. A $9,000 roof sits outside NOI by convention. It still leaves your bank account. Run the reserve below the line and judge the purchase on cash flow after reserves, not on cap rate alone.
• Tax reassessment after sale is easy to miss. In many jurisdictions a sale triggers a reassessment toward the purchase price. If the seller's tax line reflects an old assessment, your expense stack is understated from day one. Ask, and model the post-sale figure.

The discipline is the same one that runs through the yield guide: rerun the formula on pessimistic inputs, not average ones, and see whether the purchase still makes sense to you.

Cap rate vs yield vs cash flow vs return

Four numbers get confused constantly, and each has one job:

Total return sits beyond all four: it adds value growth or loss, principal repaid, and tax effects across the whole holding period, and it can only be known afterward. A listing that quotes only the most flattering of these numbers is telling you which one to ask about. Ask about that one, out loud, with the worksheet open.

Cap rate also differs from an internal rate of return (IRR) or yield-to-maturity style measure in an important way: it is a one-year snapshot that ignores the time value of money, future rent growth, and the eventual sale. Two properties at the same cap rate can have very different multi-year returns if one sits in a growing rent market and the other faces a major lease expiry. Use cap rate to compare and to price income. Use a multi-year cash-flow model, with your real financing, to decide.

Four cap-rate mistakes that flatter bad purchases

1. Capitalizing the pro forma instead of the history. A seller's projected rent at full occupancy with trimmed expenses produces an NOI the property has never earned. Start from the trailing statement, verify each line, and treat every projection as a separate claim needing its own evidence.
2. Omitting the management fee you will actually pay. Self-management is labor, not magic. If your plan involves a manager, the market fee belongs in the expenses whether or not the seller paid it.
3. Comparing across unlike properties. A cap rate from a prime multi-family building and one from a small single-family rental in a different city describe different risks, tenant bases, and exit buyers. Compare like with like, on the same NOI definition, or do not compare at all.
4. Reading a high cap rate as a bargain by itself. Higher cap rates commonly price in higher risk: weaker location, shorter leases, deferred maintenance, or softer rent growth. Sometimes that risk is well paid. Sometimes it is just risk. The rate tells you the market's price for the income; your inspection, lease review, and reserve math tell you whether the income is real.

A buyer cap-rate checklist

1. Get the trailing twelve-month income and expense statement, plus current leases. A brochure summary is not a statement.
2. Restate rent to achievable market rent from current comparable lettings, and write down the source for each comparable.
3. Apply an explicit vacancy and credit-loss allowance, and label the percentage.
4. Rebuild the expense stack: tax (at the post-sale assessment where that applies), insurance, maintenance, management at the fee you will pay, landlord utilities, licensing.
5. Confirm what is excluded, then add a capital reserve below NOI based on roof, heating, and major-system ages.
6. Compute cap rate at the asking price. Then compute the price at which the property meets your required rate, using value = NOI / your rate.
7. Compute cash flow separately with your real deposit, rate, and term, after reserves.
8. Compare only against properties evaluated on the identical basis, and keep the worksheets. The discipline is the asset; any single percentage is not.

Getting NOI from a real seller statement without fooling yourself

In practice you rarely start from a clean formula. You start from documents a seller or listing agent hands you, and the documents decide whether the cap rate means anything. Work through them in this order.

First, the rent roll. This lists each unit, the tenant, the lease start and end, and the rent actually charged. Compare every line to the leases themselves. Rents that step up next year, concessions buried in an amendment, and a unit priced above what the last relet achieved all hide in the gap between the rent roll summary and the lease file. Cap rate capitalizes the rent the lease obligates, not the rent the brochure hopes for. If a lease expires in four months at below-market rent, your forward NOI uses the achievable market rent after relet, minus the empty weeks and reletting costs to get there.

Second, the trailing statement. Ask for the trailing twelve months of income and expenses (the T12), plus year-to-date figures. A T12 shows seasonality and one-off repairs as they actually landed. Two gaps appear constantly. Owner-paid items that will transfer to you (a lawn contract in the owner's name, insurance bundled with another property) may be missing entirely, which understates expenses. And personal items (the owner's vehicle, travel, a home-office allocation) may be included, which overstates them. Restate the statement to the property you will own, line by line, and keep a note of every line you changed and why. That note is the difference between analysis and wishful thinking.

Third, the forward pro forma. Sellers and brokers often present a stabilized forward view: market rents, standard vacancy, tidy expenses. A pro forma is not dishonest by definition, but it is an argument, and arguments get checked. The three lines to stress first are rent (is it signed or aspirational), vacancy (is any allowed at all), and management (is the fee you will pay in there). If any of the three flatters the property, rebuild NOI from the T12 and leases and use the pro forma only as a list of claims to test.

A useful habit: compute two NOIs. The in-place NOI uses signed rents and restated actual expenses. The stabilized NOI uses achievable market rents and your planned expense stack. Price the purchase on the in-place figure, and treat any gap to the stabilized figure as work you are paying for in time, vacancy, and reletting cost. Buyers who capitalize the stabilized figure at the asking price have paid the seller for improvements the buyer still has to make.

Single-family houses and small rentals: same math, weaker signal

Cap rate was built for commercial and multi-family property, where buyers pay for income and income sets the price. A single-family rental lives in two markets at once: investors price it on rent, and owner-occupiers price it on schools, lot, condition, and the house next door. That second market is why two rentals with identical cap rates can have very different resale paths, and why a house can trade at a cap rate that looks poor against an apartment building while still being the stronger purchase for appreciation or exit flexibility.

None of that breaks the calculation. It limits what the result can tell you. For a house or a duplex, use cap rate to answer the screening question (does the income justify further work on this listing at this price) and the comparison question (evaluated identically, which of these three rentals keeps the most operating income). Do not use it to answer the valuation question alone, because no house buyer at resale will price your exit purely on NOI. Condition, permit history, lot, and neighborhood comparables will carry at least as much weight, and your inspection budget should reflect that order.

Small portfolios add one more wrinkle: expense lumpiness. In a twenty-unit building, one empty unit is a 5 percent vacancy problem. In a single rental, one empty month is an 8 percent revenue event and a water heater is a year of maintenance budget at once. The formulas handle this fine. Your vacancy allowance and your capital reserve have to be sized for a portfolio of one, which means more conservative than the building down the street, not less.

A sensitivity table you can copy

Percentages hide how fragile the inputs are. Before you offer, rerun the worked-example structure with your own pessimistic and optimistic cases side by side. The table below keeps the hypothetical $425,000 asking price and changes only the inputs, so you can see which assumption does the damage.

Read the rows as a warning about precision. The seller-view row (management deleted) and the softer-rent row differ by a full point of cap rate on the same building at the same price, using nothing more exotic than whether a fee is counted and whether a rent is real. This is why two careful analysts can quote different cap rates for one property without either one lying: they made different, stated assumptions. Your job is to make yours explicit, defend each one with a lease, a bill, or a comparable, and refuse to compare your conservative NOI against someone else's optimistic one.

The same table teaches the negotiation use. If the verified rows cluster near 4.4 percent and your required return is 5 percent, the formula gives you the price that closes the gap: value = NOI / 0.05. On the harder-vacancy NOI of $18,692, that price is about $373,840. You may still choose to pay more for growth, condition, or location reasons, but you will be doing it knowingly, with the income shortfall priced, rather than discovering it in year two.

Where the formulas come from

The cap rate definition used here (net operating income divided by current market value, expressed as a percentage) and the NOI construction (effective income minus operating expenses, excluding mortgage and debt service) follow published real estate investment references, including LoopNet's investor guide to cap rates (divide annual NOI by market value or purchase price, with mortgage payments and income taxes excluded because cap rate measures the property's income before financing), Accounting Insights' commercial real estate explainer (NOI from gross income minus operating expenses such as maintenance, insurance, and management, excluding mortgage payments and capital expenditures), and PayRent's cap rate calculator guide (cap rate = NOI / property value x 100, with vacancy-aware income and annual figures for consistency). The worked example's inputs are this site's own labeled hypotheticals, not figures from those sources or any market.

What the limits are

Cap rate is a useful, limited tool: an exact division performed on estimated inputs. It will happily price a fiction if you hand it one. The investors who get hurt by this calculation are rarely wrong in the division. They are wrong in the vacancy they assumed, the fee they deleted, the tax line they never restated, or the reserve they never funded. Build NOI from history, state every assumption on the worksheet, reverse the formula to find the price your required return actually supports, and let the percentage do the two jobs it is good at: comparing income properties on equal terms, and pricing an income stream you have verified is real.

This guide is educational content about a calculation. It is not financial, tax, or legal advice, and it does not recommend any property, market, or purchase. For decisions with real money attached, work with a qualified local appraiser, inspector, lender, and advisor who can see the actual leases and statements.