GRM = price ÷ annual rent. Lower is generally better — a quick screen, not a full analysis.
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What does this calculator estimate?
A gross rent multiplier (GRM) is a screening ratio that compares a property's price to the rent it collects. GRM = property price / annual gross rental income, where gross means rent before vacancy, expenses, or taxes are deducted. The annual figure usually comes from multiplying the monthly rent by 12. For example, a $300,000 property renting for $2,000 a month collects $24,000 a year, so GRM = 300000 / 24000 = 12.5. Lower GRM generally means more rent collected per dollar of price, so lower is generally better when comparing similar properties in the same market. GRM is a screening tool, not a full valuation: it deliberately ignores operating expenses, vacancy, and taxes, and it should not be used in isolation.
- GRM = property price / annual gross rental income; rent is usually entered monthly and annualized by multiplying by 12. (Source: CFI, 'Gross Rent Multiplier (GRM)' — corporatefinanceinstitute.com)
- Gross rental income is rent before vacancy, management fees, taxes, insurance, and other operating expenses are deducted, so GRM measures what you pay per rent dollar, not net profitability. (Source: CFI, 'Gross Rent Multiplier (GRM)' — corporatefinanceinstitute.com)
- There is no single universal 'good' GRM number; it is meaningful only relative to comparable properties in the same market and asset class. Lower GRM generally indicates more rent per dollar of price. (Source: CFI, 'Gross Rent Multiplier (GRM)' — corporatefinanceinstitute.com)
- GRM is a back-of-envelope screening tool and should not be used in isolation; it cannot by itself confirm that a property is a good investment because it ignores expenses and vacancy. (Source: CFI, 'Gross Rent Multiplier (GRM)' — corporatefinanceinstitute.com)
GRM versus cap rate: when each number is safe to trust
GRM divides price by annual gross rent and deliberately knows nothing about expenses. Cap rate divides net operating income by price and therefore requires you to know taxes, insurance, water, common electric, vacancy, and management costs. The two move in opposite directions under different conditions. In a high-tax jurisdiction with expensive utilities, two buildings with identical GRM can carry cap rates 1.5 points apart: a $500,000 duplex at $48,000 gross has GRM 10.4 either way, but $22,000 of expenses yields cap rate 5.2% while $12,000 of expenses yields 7.2%. Gross tells you what you pay per rent dollar; cap rate tells you what survives.
Use GRM at the top of the funnel, when you have the asking price but no rent roll, or when comparing across markets where expense structures differ and you plan to underwrite your own anyway. Use cap rate at the bottom of the funnel, once you have seen the estoppel statements, the actual tax bills, and the utility accounts. Investors who screen with cap rates get filtered by bad data they invented themselves, because they guessed an expense ratio. Investors who screen with GRM lose nothing: they simply refuse to pass along a number they cannot defend, and revisit the survivors with real documents.
Rent comps decide the multiplier more than the building does
The same duplex in two neighborhoods 400 yards apart can have identical construction and a GRM gap of 3 full points, purely from what similar units rent for. A three-bedroom at $1,500 in an Area A comps area and $1,800 across the line means the second building's GRM is 20% lower for the same price basis, and so is your future cash-on-cash return. The unit that looks overpriced at a glance is often the one with upside if local rents are about to jump; the one that looks cheap is often surrounded by $900 three-bedrooms, priced correctly.
This means the calculator's output is only as good as the rent number you feed it, and the rent number is the one input investors consistently overestimate. Pull three to five comps in the same building class within the same school zone, not the same city. Subtract nothing for vacancy here; GRM is a gross metric by design. Then hold the market's typical GRM constant and rank buildings by the rent they can plausibly achieve, not the rent the current owner is charging. A building with below-market leases in place will show a misleadingly high GRM for 12 to 24 months until the leases expire, and this is the single biggest trap in using the tool at all.
Why in-place leases can make a good building look bad
Multiply price by the current rent roll and you get a number that says almost nothing about the next owner's first year.Whenever every lease is $150 below market, computed GRM is inflated, and the building looks expensive. The correct input for screening is achievable market rent, not contract rent, because GRM is a screening number: it is comparing instruments that could all be bought today at current market conditions.
This is also why a turnover-heavy building can look attractively priced when it is not. Two $600,000 buildings, both at $54,000 annual gross, screen as identical GRM 11.1. In one, every lease was written last month at market; in the other, 80% of tenants are paying rents that expired below market two years ago. The first is a real GRM 11.1. The second's achievable rent is more like $60,000, and its true GRM is 10.0 once leases roll, so beside-based screening will overvalue the second building. Ask for a rent roll with lease end dates. Buildings where a meaningful share of leases expire in the next six months are the ones where contract-versus-market confusion bites hardest.
Using GRM to screen a portfolio: a realistic workflow
The multiplier earns its keep as a rejection tool, not a buying tool. Suppose you are scanning an MLS with 40 multifamily listings. Assign the going local GRM for that asset class, say 10.5 for two-to-four unit buildings in a mid-cost market (an illustrative figure; yours should come from closed deals that closed under 12 months ago). Anything with a GRM worse than about 12.5 gets cut immediately, because no rental economics make a 12.5 GRM work in a market where 10.5 is normal. Anything under 8.5 gets a second look for the wrong reasons: it is usually a problem asset, a zone where yours does not belong, or a listing with a rent roll nobody is showing you.
That leaves maybe 8 properties in the middle band, and that is where the actual underwriting begins: get the rent roll, the tax bill, the insurance quote, and the utility bills, and compute cap rate properly on those. Expect to spend 30 minutes each. Expect to eliminate half. The point is not that GRM is precise; it is that rejecting 32 of 40 properties in 90 seconds of tabulation is worth more than an hour of careful work on a building no economist would ever underwrite. The calculator's job in this workflow is to tell you how fast to move on, which is a different job than telling you what to pay.
How this calculator works
Formula
GRM = property price / annual gross rental income, where annual gross rental income is the monthly gross rent multiplied by 12.
Assumptions to verify
- The rent you enter is the monthly figure. Annualising it twice, or entering an annual rent, will skew the ratio by a factor of twelve.
- Gross rent means before vacancy, management, repairs, taxes and insurance, so the multiplier says nothing about cash flow.
- The price is the purchase price. Closing costs, capital improvements and any debt on the property are excluded.
- A purchase price with no rent, or a rent with no price, produces no usable multiplier; the tool needs both.
Frequently asked questions
How do you calculate gross rent multiplier?
Find the property's annual gross rental income first, by multiplying the monthly gross rent by 12. Divide the property price by that annual figure to get GRM. For example, a $300,000 property renting for $2,000 a month collects $24,000 a year, and 300000 / 24000 = GRM 12.5. Interpret the result by comparing it against comparable properties in the same market: a lower GRM means you pay less per rent dollar, but it is a screening signal only, not a measure of net cash flow.
Cite this tool
BoringToolsKit. “Gross Rent Multiplier Calculator.” boringtoolskit.com/gross-rent-multiplier-calculator/. Free to reference in articles, syllabi, and answer posts with a link.
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