The 50% rule is defined as an estimate that roughly half of a rental property’s gross rent goes to operating expenses over a long hold, before the mortgage payment. A property renting for $2,000 a month should budget about $1,000 for taxes, insurance, repairs, vacancy, and turnover, leaving $1,000 to cover principal and interest.
I use the 50% rule the same way I use the 1% rule and cap rate: a ten-second gut check before I spend an hour building a real spreadsheet. Here’s the formula, where the number comes from, and where it breaks.
50% rule formula and worked example
Operating expenses are about 50% of gross rent. On $2,000 a month, budget $1,000 for expenses; the other $1,000 must cover principal and interest.
Operating expenses ≈ 50% of gross rent
Subtract that from your rent, and what’s left needs to cover the mortgage principal and interest. If it’s more than your P&I payment, the deal has a shot. If it’s less, you’re subsidizing the property out of your own pocket every month.
A worked example on $2,000 of rent
Worked example: a property renting for $2,000 a month. The 50% rule sets operating costs at about $1,000 a month, leaving $1,000 to cover the loan payment. If the mortgage P&I is $850, there’s a small cushion. If it’s $1,300, the rule is flagging a deal that loses about $300 a month before you’ve priced a single repair.
The value isn’t precision, it’s catching a bad assumption before you’ve fallen for a listing.
Why the 50% rule uses half of rent
The 50% figure is a long-run landlord rule of thumb sized to absorb outlier years, a roof, a furnace, months of vacancy, not any single year’s bills.
Where the 50% figure comes from
The 50% figure is a long-standing landlord rule of thumb rather than a measured average, and it is not meant to describe any one property’s bills in a given year. In a typical year, a rental doesn’t spend half its rent on expenses; most years run cheaper. It’s the outlier years, a roof, a furnace, three months of vacancy between tenants, that the 50% figure is sized to absorb over a 10- or 20-year hold. The rule prices in the bad years that haven’t happened to you yet.
That’s also why applying it to a single year of actual performance is a mistake. A landlord who looks at last year’s expenses, sees they ran at 30% of rent, and decides the rule is too conservative is repeating the exact error the rule exists to catch. Averages include years that haven’t happened to you yet.
What counts as a rental operating expense
Operating expenses cover taxes, insurance, repairs, vacancy, capital items, management, owner-paid utilities and turnover, never mortgage principal and interest.
The rule covers everything except the mortgage payment itself:
- Property taxes
- Insurance
- Repairs and maintenance
- Vacancy (the months a unit sits empty between tenants)
- Capital expenditures (roof, furnace, water heater, amortized over their expected life)
- Property management, if you pay for it
- Utilities you cover, plus turnover costs like cleaning and re-listing
It does not cover principal and interest on your loan. That’s the number the rule is protecting: whatever’s left after expenses needs to cover the debt payment, or the property runs cash-flow negative.
Where the 50% rule breaks down
The 50% rule overstates costs on newer buildings, understates them on old buildings in harsh climates, ignores financing, and was not built for house hacks.
Every quick screen misses in a specific, predictable way, and this one misses in at least four directions:
- Newer buildings run cheaper. A property built or fully renovated in the last decade has newer mechanicals and a roof with years left on it. Fifty percent overstates real costs, sometimes significantly, in the early years.
- Older buildings in harsh climates run worse. A hundred-year-old building somewhere with real winters, snow removal, ice dams, an aging boiler, can blow past 50% in a bad year. The rule understates that risk.
- It ignores your financing. The 50% rule only tells you what’s left to cover P&I. It says nothing about your down payment, your interest rate, or your cash-on-cash return once the mortgage is covered. Two properties can both pass the 50% screen and produce very different returns depending on how they’re financed.
Why it does not fit an owner-occupied house hack
The rule assumes a straight rental: you buy it, someone else lives in all of it, and every dollar of rent is income compared against 100% of the expenses. A house hack changes that math, because you’re living in part of the building and comparing the deal against what you’d otherwise pay in rent, not a market return on a pure investment.
How the 50% rule lands on my own duplex
On my own duplex, my upstairs tenant covers around $1,200 a month toward a PITI payment near $2,880, and the basement adds Airbnb income on top of that. Run that setup through a straight investor lens and the 50% rule doesn’t map cleanly, because I’m not comparing rent to expenses on 100% of the building, I’m comparing my own housing cost before and after. If you’re evaluating a house hack specifically, effective housing cost is the more useful number to build your decision around; the 50% rule is built for the classic all-tenants-no-owner case.
50% rule vs. 1% rule vs. cap rate vs. cash-on-cash
The 50% rule shows how much rent survives to cover the mortgage; the 1% rule, cap rate and cash-on-cash answer different questions. Run all four.
How the 50% rule sits beside the other screens
The 50% rule isn’t meant to work alone. It answers one narrow question, how much of the rent survives to cover the mortgage, and leaves other questions to other screens. The 1% rule answers a faster, cruder version of the same question using price instead of a real expense estimate. Cap rate answers a related but different question: how does this building’s income compare to another building’s, independent of financing. Cash-on-cash answers the question that actually decides whether the deal is worth doing: what your invested cash returns once the mortgage and expenses are both accounted for.
Run a listing through all four and the read is more reliable than any single screen. Run the screens together, then set them aside in favor of the property’s actual numbers once something survives all four.
How to use the 50% rule step by step
Screen with the 1% rule first, apply the 50% rule to survivors, then replace both with the property’s actual tax bill, insurance quote and repair reserve.
- Run the 1% rule first. If monthly rent is nowhere near 1% of price, I don’t spend much more time on it.
- Apply the 50% rule to whatever survives. If half the rent doesn’t comfortably cover the mortgage, the deal needs a specific reason to keep going: a below-market purchase price, unusually low property taxes, something concrete.
- If it still looks interesting, build the numbers that matter: actual tax bill, actual insurance quote, a repair reserve sized to that property’s age and condition, not an average.
Screens are for saying no quickly. Say yes only after you’ve priced the property’s own numbers, not the rule of thumb’s.
Frequently asked questions
What is the 50% rule in real estate?
The 50% rule is defined as a guideline stating that roughly half of a rental property’s gross rent, over the long run, goes to operating expenses such as taxes, insurance, repairs, vacancy, and capital costs, before the mortgage payment.
Does the 50% rule include the mortgage payment?
No. The 50% rule covers operating expenses only. Whatever is left after that 50% is what has to cover your mortgage principal and interest; the rule does not include P&I in the 50%.
Is the 50% rule accurate for a house hack?
The 50% rule is built for a fully tenanted rental and is only a rough fit for an owner-occupied house hack, because a house hacker is comparing housing cost saved, not income against 100% of expenses. Effective housing cost is the more direct metric for that case.
Run it on a real listing
A free house hacking calculator turns a listing’s price, rent and loan terms into a real monthly cost in seconds, with no account or email required.
The fastest way to see this in action is to run an actual property through it instead of a hypothetical. The free house hacking calculator takes a price, a rent, and your loan terms and returns your real monthly cost in a few seconds, no account, no email required.
For the mechanics behind cash flow and expenses in more depth, see how to calculate cash flow on a rental property, step by step.
Keep going
- What is house hacking? A plain-English guide
- How to calculate cash flow on a rental property, step by step
- Effective housing cost: the one number house hackers should track
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Sources
Rule-of-thumb figures (50% expense ratio, typical range) reflect common landlord industry conventions; treat as a screen, not a guarantee, and price your own building’s actual taxes, insurance, and repair history.
I’m not a CPA or a financial advisor, just someone who runs these numbers on my own properties and shares what I find. Verify anything specific to your situation with your own lender or accountant.
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