The 1% Rule and GRM

Two five-second screens

There are two numbers you can run on a listing in about five seconds each, and both are useful for exactly one thing: deciding whether a property is worth a real analysis. Neither is a real analysis.

The first is the rent-to-value ratio, better known as the "1% rule": monthly rent ÷ price. If a $200,000 house rents for $2,000, that's 1.0% — the rule of thumb says properties near or above 1% are "worth a look," and those well below it often aren't. The second is the gross rent multiplier (GRM): price ÷ gross annual rent — how many years of gross rent it would take to equal the price. A lower GRM means cheaper relative to gross rent; a higher GRM, more expensive. Both are one division. Both let you scan a page of listings and rank them fast.

What both screens leave out

Here's what they have in common, and why it matters: both use only rent and price. Nothing else. No property taxes, no insurance, no vacancy, no management, no maintenance, no condition, no financing. Everything the full underwrite builds — effective rent, the expense stack, net operating income (NOI), cap rate, cash-on-cash, the debt-service coverage ratio (DSCR) — is invisible to these screens. (NOI is what the property earns after operating costs and before loan payments.) And those invisible things are much of what determines the deal's economics. Property-tax burdens can vary materially across jurisdictions; a property at "1%" in a high-tax, high-vacancy market can be a worse deal than one at 0.8% in a low-tax, stable one. The screen can't see the difference. That's not a flaw to fix; it's the nature of a screen.

Two screens, one relationship

In fact, the two screens aren't even independent evidence. Look at the definitions: the 1% ratio is monthly rent ÷ price, and GRM is price ÷ annual rent. Since annual rent is just monthly rent × 12, GRM works out to 1 ÷ (12 × the rent-to-price ratio) — the two are inverse transformations of the same price/rent inputs. The 1% rule asks "how much monthly rent do I get per dollar of price?"; GRM flips it to "how many years of gross rent equal the price?" They look like two metrics, but they package one relationship two ways — which is exactly why they share identical blind spots. Running both doesn't double-check anything; it restates the same fact. (One convention note: some versions of the 1% rule add immediate rehab to the denominator. These guides use monthly rent ÷ purchase price consistently — screens need consistent conventions just like the real metrics do.)

The example rental through both screens

Run the example rental these guides use through the 1% rule and the limitation shows up right away. (It is an illustration; its full assumption set is listed in The Operating-Expense Build & the 50% Rule.) Monthly rent is $2,200 on a $280,000 price, so rent-to-value is 0.79% — comfortably below 1%. A strict "1% rule" investor would deprioritize or reject it on sight, without ever seeing the full economics.

But here's the careful way to say what the underwrite showed. It's not that "the screen was wrong." It's that the property is a deliberately thin, near-break-even hold rather than an obviously nonsensical deal — and the screen cannot make that distinction. The 0.79% tells you almost nothing about why the deal is thin or whether that thinness is acceptable for a given investor; only the full underwrite (and the buy/pass decision that follows) can answer that.

The reverse can happen too: a property can clear the 1% screen and still fall apart once real taxes, vacancy, management, maintenance, financing, and a reserve are modeled. The screen's real problem isn't that it gives wrong answers — it's that it can't know whether its answer is right.

Its GRM tells the same story from the price side: $280,000 ÷ $26,400 = 10.6. That's a tidy number for comparing this listing to others on gross rent, but it's blind to the fact that two properties with the same GRM can have radically different expense structures — and the expense structure determines how much of the gross rent actually survives. GRM ranks price against gross rent; it says nothing about what's left after the bills.

Screen first, then underwrite

So use screens for what they're good at: triage. When you're staring at forty listings, the 1% rule and GRM let you deprioritize the least promising and rank the rest, so you spend your real underwriting time on the most promising candidates first. Then — and this is the whole discipline — you underwrite the survivors properly: Effective Rent & Economic Vacancy, the full expense build, Normalized NOI & Cap Rate, Cash-on-Cash Return, Analytical DSCR, and the buy/pass decision in Does This Rental Pencil?. The screen narrows the field; the underwrite makes the call. Buying on a screen is buying a deal you haven't actually analyzed.

The 1% rule and GRM are fast, cheap, and genuinely useful for sorting listings — and useless as a final answer, because they ignore the economic inputs that separate a good deal from a bad one at the same rent and price. Screen to decide what's worth your time; underwrite to decide what's worth your money. The example rental fails a strict 1% screen, yet the full underwrite reveals a far more nuanced economic picture than "0.79%" could — which is exactly why you run the analysis, and exactly what the buy/pass decision is for.