Calculator
Rental Property Calculator
Rental Property Calculator
Taxes, insurance, maintenance, HOA, property management — exclude mortgage principal and interest.
Monthly Cash Flow
$65.17
Property Analysis
The property cash-flows $65.17/month — positive, but a 0.8% cash-on-cash return is thin after accounting for repairs, turnover, and your management time. The 6.2% cap rate and 11.5% first-year total return (with appreciation) improve the picture, yet the hurdle for most rental investors is 8%+ cash-on-cash. Pushing rent, trimming financing cost, or negotiating the price are the three levers worth testing in this calculator.
*Estimates cash flow, cap rate, and cash-on-cash return using user assumptions, with 3% purchase closing costs and a 30-year amortizing loan model. Does not include income taxes, depreciation benefits, or capex. Educational only, not investment advice.
Underwriting a Rental Before You Buy
Rental real estate remains one of the most popular wealth-building vehicles in the United States — combining cash flow, loan paydown, tax advantages, and appreciation into a single asset. Individual investors hold the majority of American rental housing, and the appeal is obvious: a modest down payment can control an appreciating asset whose tenant effectively retires the debt. But the distance between a good rental and a bad one is not visible in the listing photos; it lives in the math, and the math is merciless about inputs. Professional underwriting distills to a handful of numbers. The cap rate — net operating income divided by price — strips out financing to compare the property's raw earning power across markets. Cash-on-cash return measures the annual pre-tax cash flow against the cash actually invested, and it is the number that tells you whether your money is working harder here than it would in an index fund. Cash flow, the monthly surplus after every expense and debt payment, is what keeps the property from becoming a liability the first time a furnace dies. Most failed rentals were purchased on emotion — the beautiful kitchen, the 'it'll appreciate' story — with the three numbers never honestly computed. This calculator computes all three before you ever write an offer, so the property competes on merit against every other place your capital could go.
From Rent to Cap Rate to Cash-on-Cash
The waterfall starts with gross annual rent and trims vacancy — an allowance (typically 5–8%) for the weeks a year the unit sits empty, because rents at 100% occupancy are a fantasy in almost every market. What remains is effective gross income; from it, annual operating expenses (taxes, insurance, maintenance, management, HOA) are subtracted to produce net operating income, or NOI — the property's earnings before any financing. Cap rate is simply NOI ÷ purchase price: the financing-free yield that lets you compare this property against any other property or market regardless of how it is bought. Then financing enters: the down payment plus closing costs form your cash invested, and the mortgage — priced with standard amortization math at your rate and term — produces the monthly payment. NOI minus annual debt service is cash flow, and cash flow ÷ cash invested is the cash-on-cash return. The reported first-year total return adds appreciation on the full property value to cash flow — the leverage effect that makes rental returns larger than their cash yield, and cuts the other way when values fall. Every assumption is adjustable, because underwriting is nothing more than honest inputs through this waterfall.
Expert Insights
The 1% Rule Is a Screening Heuristic, Not a Law
The classic heuristic — monthly rent at or above 1% of the purchase price — has grown harder to hit in high-price markets, but it remains a useful first filter for cash-flow potential: a $350,000 property rents for about $3,500 monthly would clear it, while most coastal metros never come close. The rule's real purpose is speed: it kills bad deals in five seconds before you spend hours underwriting them. In expensive markets the bar shifts to ~0.7–0.8%, but anything substantially below that means you are paying for appreciation, not income — a bet, not a rental business. Use it as the door; use the calculator as the verdict.
Underwrite Expenses Like Someone Who Has Owned
New investors chronically undercount operating costs: property taxes rise after sale, insurance reprices at renewal, roofs and HVACs amortize into repair reserves, and property management takes 8–10% of rent if you are not self-managing. A defensible expense model budgets tax, insurance, 4–8% of rent for maintenance, the vacancy allowance, and management — and treats anything left as the true profit. Sellers' pro formas routinely understate these, since they want the deal to pencil. Pull actual tax bills, quote fresh insurance, and assume the water heater dies in year two; the property you underwrite conservatively is the one you can hold through a bad year.
Cash Flow and Appreciation Are Different Bets
A property can cash-flow today and still be a mediocre investment, or cash-flow negatively and still win via appreciation in a scarce market — but you should know which bet you are making. Positive cash flow with modest appreciation is a yield investment; negative cash flow banking on price growth is speculation with a monthly carrying cost. The sustainable stance for most individual investors is cash flow first: a property that covers its own debts and reserves is holdable through any market, while an appreciation-dependent property forces a sale in exactly the downturn when prices are worst. Decide which side you are on before you buy, not after.
Actionable Tips
- 1
Verify the Rent With Real Comps
Never underwrite on the seller's stated rent alone. Pull comparable listings and recent leases for the same unit type in the same neighborhood — actual signed rents, not asking rents. If the current tenant is under market, confirm the market number independently; if over, question it. A $150/month rent error compounds to $1,800 a year and can flip a deal from positive to negative. The calculator's output is only as real as the rent you feed it, and the rent is the single easiest number to get wrong when you want the deal to work.
- 2
Build a Capex Reserve Into the Monthly Number
Budget explicitly for capital expenditures: a roof every 15–25 years, HVAC every 10–15, appliances on their own schedules. As a rule of thumb, set aside $100–$200 per month beyond operating expenses, or a fixed percentage of rent, into a property reserve account from day one. The investors who get hurt are rarely sunk by vacancy; they are sunk by a $9,000 roof in the same year the furnace fails, with no reserve to absorb it. A property that cash-flows only in years when nothing breaks is not cash-flowing — it is borrowing from the future.
- 3
Stress-Test Vacancy, Rate, and Rent Before the Offer
Run the calculator three more times: at 10% vacancy, at a mortgage rate one point higher, and with rent 5% lower than your comp research. If the property still holds positive cash flow through all three, it has a genuine margin of safety; if it collapses under any one, the deal is thin and should pass or be re-priced. This stress test takes two minutes and filters out the deals that only work in the sunniest scenario. The market will eventually test your assumptions anyway — it is cheaper to test them yourself first.
Real-World Examples
Rosa Passed on the Pretty Duplex Because the Cap Rate Said No
Rosa loved a renovated duplex listed at $415,000 with rents of $3,100 total. The calculator gave a 5.1% cap rate and slightly negative cash flow after her actual expense assumptions. The seller's pro forma had shown positive flow — it had understated taxes, insurance, and skipped vacancy and management. She passed, and the buyer who paid list price was hit the following year by a reassessed tax bill and an empty unit, turning the 'turnkey income property' into a monthly drain. Rosa bought a plainer triplex at a 7.4% cap rate three months later; it has cash-flowed every year since. The calculator did not buy her property, but it vetoed the one that would have cost her.
Marcus Turned One Good Property Into Four
Marcus's first rental was a $280,000 single-family home renting at $2,350 — the calculator showed a 7.2% cap rate, $310/month cash flow, and 9.8% cash-on-cash on his 25% down. He self-managed, banked the flow into a dedicated account, and when the property appreciated enough to re-leverage conservatively, the reserve plus equity became the down payment for a second, then a third. Each purchase went through the same underwriting gauntlet; he rejected eleven deals for every one he bought. Ten years on, the four properties cash-flow over $1,700 a month combined, and his discipline was the compounding ingredient the spreadsheet could not supply.
The Lims Held Through the Vacancy Because They Had Run the Numbers
When the Lims' tenant left after four years, the unit sat empty for nine weeks. Because their purchase underwriting had included an 8% vacancy allowance and a funded reserve, the gap was absorbed without drama — the reserve covered the mortgage and a paint-and-carpet refresh. They had stress-tested a 10% vacancy before buying, and reality landed inside the model. Friends who had bought a flashier property with no allowance and no reserve spent the same summer covering their mortgage from personal savings. The difference was not luck; it was that the Lims had underwritten the bad months before they happened.
Glossary of Terms
- Cap Rate
- Net operating income divided by purchase price — the property's unlevered annual yield. It strips out financing so properties and markets can be compared on earning power alone.
- Cash-on-Cash Return
- Annual pre-tax cash flow divided by the cash invested (down payment plus closing costs). It answers the investor's real question: what is each dollar I put in producing each year?
- Net Operating Income (NOI)
- Effective rental income (after vacancy) minus operating expenses, before mortgage payments. It is the property's true operating earnings and the input to the cap rate.
Frequently Asked Questions
Everything you need to know about this topic.
Ivy Sinclair-Wren
Financial Chaos Analyst
Ivy Sinclair-Wren is a Financial Chaos Analyst covering investing, AI, wealth psychology, and the emotional consequences of opening finance apps during market crashes. Based in Melbourne, she specializes in demystifying the US tax code and helping users navigate the intersection of spreadsheet logic and human irrationality.