What is the 50% rule?
The 50% rule is shorthand for estimating a rental property's operating expenses without itemizing a single one. The claim: over time, everything except the mortgage — property tax, insurance, vacancy, maintenance, CapEx reserves, management — averages out to roughly half of gross rent. That gives you a three-line triage:
On a $1,900/month rental with a $1,150 P&I payment: expenses ≈ $950, NOI ≈ $950, cash flow ≈ −$200/month. Three seconds, no spreadsheet — and in this example, a useful early warning. For the full honest take on the rule, see is the 50% rule still useful in 2026?
Where the rule is genuinely accurate
The 50% rule was calibrated on a specific archetype: stabilized single-family rentals in moderate-tax, moderate-insurance markets — classic Midwest workforce housing with conventional financing and long-term tenants. For that profile, it's surprisingly good: across a portfolio and multi-year averages, vacancy + maintenance + CapEx + management + tax + insurance really does converge near half of gross rent. If that's your market, trust the rule for triage.
The five places the 50% rule lies
1. High property-tax states
Texas effective property tax can hit 2.5–3.2% in new-construction MUD suburbs. On a $300k property renting for $2,400/month, tax alone is $7,500–9,600/year — already 25–33% of gross rent before a single repair. Real expense ratios land at 60–65%, and deals that look great at 50% actually break even.
2. High-insurance markets
Post-2022 Florida insurance runs $2,500–4,500/year inland and $6–12k+ coastal. The rule was calibrated for $1–2k annual premiums; Florida routinely triples that share of rent.
3. Pre-1940 housing stock
The rule assumes a ~5–8% CapEx reserve. Century-old housing in Cleveland, Philadelphia, or Detroit routinely consumes 10–15% in real-world CapEx — roofs, electrical service, plumbing, foundations. Underwrite older buildings at a 55–60% expense ratio.
4. Short-term rentals
STRs run 60–75% of gross revenue in operating costs (per-turnover cleaning, higher insurance, 15–25% management, turnover maintenance). The 50% rule simply doesn't apply — use STR-specific underwriting.
5. High-HOA condos
A $400/month HOA on a $1,800/month rental is 22% of gross rent before anything else. Add the normal expense stack and you're well past half. The widget's adjustable expense ratio exists for exactly these cases — but past 60%, stop adjusting the guess and get the real numbers.
How the 50% rule fits with the other screens
Rules of thumb stack. The 1% rule checks the income side — is the rent big enough relative to the price? The 50% rule checks the expense side — does the rent survive operating costs and the mortgage? A listing that clears both in under a minute has earned the full underwrite; the stricter 2% rule is the cash-flow-market variant of the income screen. From there, replace the guesses with line items: the rental cash flow calculator itemizes every expense the 50% bundle compresses, and the NOI calculator walks the formal NOI (which, unlike the rule's bundle, excludes the CapEx reserve — the convention lenders use).
Use it to filter, never to commit
The 50% rule's job is to filter out the bottom 80% of listings so your full underwrites go to the top 20%. It is not a decision tool: it can't see this property's actual tax bill, this market's insurance reality, or this building's CapEx backlog. When a deal clears the triage, run the address through TrueCap — the analyzer auto-fills state property tax, a HUD rent benchmark, and the current mortgage rate, then computes cash flow, cap rate, CoC, and DSCR from real expense lines. Five seconds for the rule, about two minutes for the real number.
Frequently asked questions
What is the 50% rule in real estate?+
A rule of thumb that says a rental property's operating expenses — everything except the mortgage payment — typically run about 50% of gross rent over time. So estimated NOI ≈ rent × 50%, and estimated cash flow is what's left after your principal-and-interest payment. It's a 3-second triage tool for deciding whether a listing deserves a real underwrite.
What counts as operating expenses in the 50% rule?+
The rule's bundle lumps together property tax, insurance, vacancy, maintenance, CapEx reserves, property management, and miscellaneous costs — everything except debt service (your mortgage payment). That's why you subtract only principal and interest after applying the rule, not tax and insurance again.
Is the 50% rule accurate?+
For a specific archetype, yes: stabilized single-family rentals in moderate-tax, moderate-insurance markets — classic Midwest workforce housing. Across a portfolio of that profile, expenses genuinely converge near half of gross rent over multi-year averages. Outside that profile, the rule can miss badly in either direction.
Where does the 50% rule fail?+
Five common failure modes: high property-tax states (Texas new-construction suburbs can run 2.5-3.2% effective tax — expenses land at 60-65% of rent), high-insurance markets (post-2022 Florida), pre-1940 housing stock (real-world CapEx runs 10-15% of rent, not 5-8%), short-term rentals (operating costs hit 60-75% of revenue), and high-HOA condos (a $400/month HOA is already 22% of a $1,800 rent). In those cases raise the expense ratio to 55-65% — or skip the guess and use real numbers.
Is the 50% rule's NOI the same as a formal NOI?+
Not exactly. The rule's expense bundle includes the CapEx reserve; the formal NOI convention used by lenders (and by TrueCap's full analyzer) excludes CapEx as a below-the-line reserve. For a 3-second screen the difference doesn't matter; for a real underwrite it does — which is one more reason the rule is a filter, not a verdict.
What's the difference between the 50% rule and the 1% rule?+
They screen different things. The 1% rule checks whether the rent is big enough relative to the price (income screen). The 50% rule checks whether the rent survives expenses and the mortgage (expense screen). They stack well: a property that passes the 1% rule and still shows positive cash flow under the 50% rule is a strong candidate for a full underwrite.