The gross rent multiplier is the fastest screen in rental investing: one division tells you how many years of gross rent equal the purchase price. It is a ranking tool, not a full valuation, and used that way it saves hours.
How it works
GRM = property price / annual gross rent. Annual gross rent is monthly rent times 12, before vacancies and expenses. A lower GRM means you pay less for each dollar of rent. The formula also runs backwards: maximum price = target GRM x annual rent, and required rent = price / target GRM. Always compare GRMs within the same market, because a good GRM in one city is ordinary in another.
Step by step
- Write down the property price.
- Write down monthly gross rent for all units and multiply by 12.
- Divide price by annual rent for the GRM.
- Repeat for each comparable property in the same area.
- Rank them: lower GRM is cheaper per dollar of rent, all else equal.
- Reverse the formula to set a maximum offer at your target GRM.
Worked example
Property A costs $400,000 and rents for $50,000 a year. GRM = 400,000 / 50,000 = 8.0. Property B costs $360,000 and rents for $60,000 a year. GRM = 360,000 / 60,000 = 6.0. Property B is cheaper per dollar of rent. At a target GRM of 7, the rent of $50,000 supports a maximum price of 7 x 50,000 = $350,000, so property A looks overpriced at $400,000 on this screen.
Common mistakes
- Using monthly rent instead of annual rent, which gives a GRM twelve times too large.
- Using asking rent instead of actual collected rent.
- Treating GRM as a full valuation. It ignores taxes, insurance, maintenance, and vacancies.
- Comparing GRMs across different cities or property types as if they meant the same thing.
Try it with the free tool
You can follow every step above by hand, but the free tool below does the same calculation instantly. Try your own numbers in it, then check one result by hand so you trust the method as well as the answer. Open the full tool here: open the tool.
Checklist before you finish
- Write down every input number first, with its unit, before you calculate anything.
- Work through the steps in order, and do not skip the unit conversions.
- Check the answer against the worked example above: is it the right size, and does the direction make sense?
- Round only at the end, and keep the unrounded figure for any follow-up calculation.
Practice with your own numbers
Pick three cases of your own and work each one by hand. First, try a simple round-number case you can check mentally. Second, try a realistic case with awkward numbers, the kind you will actually meet. Third, try an edge case, such as a very small or very large input, and confirm the answer still behaves sensibly. If any case gives a surprising result, re-check the units and the formula step by step before you trust it.
If your answer looks wrong
Most errors come from a small set of causes. Check that you used the same units throughout, that you divided where the formula divides and multiplied where it multiplies, and that you applied any percentage as a decimal. Check the order of operations: powers and brackets come before multiplication and division, which come before addition and subtraction. Finally, test the method on the worked example in this guide. If your method reproduces the example answer, the method is right and the inputs deserve a second look.
Quick tips
After the GRM screen, run a cap rate with real expenses on the survivors. A low GRM with high expenses can be a worse deal than a higher GRM with low expenses.