Cap rate is net operating income divided by property value, and it deliberately excludes your mortgage payment. Gross rent multiplier is price divided by annual gross rent, before any expenses. One is the property’s unlevered return, the other a five-second price screen, and neither can tell you whether your financed deal makes money.
Those three sentences resolve most of the confusion that fills investing forums about these metrics, and the rest of the confusion comes from using one number where three are needed. This guide defines each metric cleanly, builds an NOI line by line with the cap rate calculator, and runs one property through all three lenses, every figure engine-computed, so you can see exactly what each one hides. For the strategy question of how rentals actually make money, the companion piece is is the 1 percent rule dead; this page is the metrics reference it leans on.
What is a cap rate?
Cap rate, short for capitalization rate, is the property’s annual net operating income divided by its value or price. As a formula:
Cap rate = NOI / property value
On the calculator’s defaults, a 350,000 dollar property producing 18,418.80 dollars of NOI carries a cap rate of 5.26 percent. Read it as the yield the building itself would produce if you bought it outright with cash: no loan, no lender, just the property’s income against its price.
The formula also runs backwards, which is how professionals actually use it: fix the cap rate you require and the NOI implies the price. The calculator does this too. At the default 6 percent target, the same 18,418.80 dollars of NOI prices the property at 306,980 dollars, engine-computed, which is a polite way of saying the 350,000 dollar asking price only makes sense for buyers who accept 5.26. That two-way relationship, income to price and price to income, is the entire mechanism, and per JPMorgan’s industry explainer, it is how income property is compared and priced across markets.
Does cap rate include the mortgage?
No. Cap rate excludes the mortgage on purpose, and this single fact resolves the most-asked beginner question about the metric. NOI stops at operating expenses; debt service, the principal and interest on your loan, never enters the calculation.
The exclusion is a feature, not an oversight. Your financing is a fact about you: your down payment, your credit, your rate. The cap rate is meant to be a fact about the property, the same number for a cash buyer, a 25 percent down borrower, and a fund. Strip the debt out and everyone can compare the same asset on the same basis, which is precisely what a market needs from a pricing metric.
The corollary cuts the other way and matters just as much: because the cap rate never saw your loan, it cannot tell you whether the financed deal works for you. A property with a perfectly respectable cap rate can lose money every month once the payment lands. That question belongs to cash-on-cash return and DSCR, the levered metrics, and the worked example below shows how differently they can grade the same building.
What is a good cap rate?
There is no single good number, and anyone quoting one without naming a market and asset class is compressing away the information that matters. Cap rates vary with location, property condition and class, tenant quality, and the broader rate environment; JPMorgan’s explainer lists exactly these drivers, and notes that rate conditions feed through to cap rates because the cost of borrowing shapes what buyers pay. Expensive coastal markets routinely trade at low cap rates that shock investors from cheaper metros, and the same building would price differently in each.
The productive uses are comparative and directional. Compare candidates within the same market and class, where the metric is genuinely apples to apples. Ask why an outlier is an outlier, because an unusually high cap rate is usually the market pricing risk you have not found yet, not a bargain the market missed. And use the target-cap-rate mechanic to turn your own required return into a maximum price, the way the calculator’s implied-value output does, rather than arguing with the listing.
What is gross rent multiplier, and how is it different from cap rate?
Gross rent multiplier is the purchase price divided by the annual gross rent, before any expenses. As a formula:
GRM = price / gross annual rent
The word gross is the whole story. Per JPMorgan’s GRM explainer, the gross in GRM means it includes all rent payments without any deductions, and the formula does not factor in operating expenses. No vacancy, no taxes, no maintenance, no management, and certainly no mortgage. That makes GRM the fastest screen in real estate: on the GRM calculator’s defaults, a 245,000 dollar property renting for 2,500 dollars a month is 245,000 over 30,000, a GRM of 8.17, and lower means cheaper relative to the rent it produces. The same engine run shows rent at 1.02 percent of price per month, which is the one percent rule screen restated, and prices the property at 210,000 dollars if your target GRM is 7.
The difference from cap rate is one word: expenses. GRM sees rent; cap rate sees what survives of the rent. A property with low taxes and a property with brutal taxes can share a GRM while their cap rates sit far apart, which is why GRM’s honest job is deciding which listings deserve the twenty minutes a real NOI takes, and nothing more.
How do you calculate NOI?
Line by line, starting from gross rent and stopping before the loan. NOI is gross scheduled income, minus a vacancy allowance, minus operating expenses: property tax, insurance, maintenance, management, and association dues where they exist. The cap rate calculator’s default build-up, engine-computed:
| Line | Amount |
|---|---|
| Gross annual rent | 31,200 dollars |
| Vacancy loss (5%) | -1,560 dollars |
| Operating expenses (tax, insurance, maintenance, management) | -11,221.20 dollars |
| Net operating income | 18,418.80 dollars |
| Cap rate on a 350,000 dollar value | 5.26 percent |
The boundary rules answer the usual forum questions. The mortgage is out, always. Closing costs are out, they are acquisition costs, not operations. Major capital items like roofs sit in a gray zone: strict NOI treats them as below-the-line capital expenditures, while conservative underwriters fold a replacement reserve into expenses anyway, and the honest move is simply to say which you did. What is never optional is the vacancy line: rent that assumes twelve occupied months forever is a lease-price fantasy, and it flatters the cap rate exactly when flattery is most expensive.
Cap rate vs cash-on-cash vs GRM: what does each metric miss?
Each lens includes what the previous one ignored, and the clean way to hold all three is one table:
| Metric | What it measures | What it includes | What it excludes | Best use |
|---|---|---|---|---|
| GRM | Price against gross rent | Purchase price, gross rent | All expenses, vacancy, debt | Five-second screen across listings |
| Cap rate | Unlevered property return | Vacancy, operating expenses | Debt service, capex convention varies | Comparing and pricing properties |
| Cash-on-cash | Levered cash return on your cash | Everything above, plus the loan | Appreciation, paydown, taxes | Grading your financed deal |
Now the demonstration. One property, the rental property ROI calculator’s default rental, run through all three lenses on identical inputs, every figure engine-computed, and the cap rate cross-checked to the same 4.06 percent by both the cap rate calculator and the rental ROI calculator:
A 350,000 dollar property renting for 2,200 dollars a month screens at a GRM of 13.26 with rent at 0.63 percent of price per month, produces 14,223.60 dollars of NOI for a 4.06 percent cap rate, and, financed with 25 percent down at 7 percent, loses 561.12 dollars a month for a cash-on-cash return of minus 6.87 percent on the 98,000 dollars invested. The deal is negative leverage in action: borrowing at a rate above the property’s 4.06 percent unlevered yield, so every borrowed dollar subtracts. The GRM hinted (13.26 is a high price for the rent), the cap rate quantified the property, and only the levered metric revealed that this particular buyer, with this particular loan, funds the deal out of pocket every month. No single number tells the whole story, and the story here is only whole at three.
Why should you not rely on any single metric?
Because each one is a deliberate simplification, and every simplification has a blind spot exactly where some deal will go wrong. GRM misses expenses, so it cannot see the tax-heavy property. Cap rate misses the loan, so it cannot see negative leverage. Cash-on-cash misses appreciation, loan paydown, and taxes, so it undersells the slow compounding that patient landlords actually get paid, a fuller picture the rental ROI calculator reports as total and annualized return alongside the cash metrics.
The working sequence is the one this page just performed: GRM to shortlist, NOI and cap rate to understand and price the property, cash-on-cash and DSCR to test the deal as you would actually finance it, covered from the lender’s side in DSCR loans explained. For which metric should carry the most weight in different strategies, and what the classic screening rules are still good for, is the 1 percent rule dead picks up where this reference stops.
Your next step
Run a real listing through both tools. The cap rate calculator builds the NOI line by line and returns the cap rate plus the implied value at your target, and the gross rent multiplier calculator gives you the screen and the one percent check in seconds. If the property survives both, grade it the way you would actually buy it, financed, in the rental property ROI calculator, and let the three lenses disagree in front of you before any of them costs you money.
This is educational information, not financial advice. The figures here are the calculators’ illustrative defaults, computed by the same engine the calculators run; cap rates and GRMs are market and asset specific, so treat every threshold you hear as a local convention rather than a rule.