Rental Property Cash Flow Calculator
Cash flow is the oxygen of a buy-and-hold rental portfolio: a property that throws off reliable monthly surplus can weather vacancies, repairs, and rate hikes, while a negative-cash-flow property quietly drains your bank account until it forces a sale. This calculator gives you an honest monthly and annual picture by starting with gross rent, discounting it for a realistic vacancy rate, and then subtracting your mortgage payment alongside operating expenses like taxes, insurance, management, and maintenance reserves. The result is the true dollar figure that lands in your pocket after the property pays for itself. New investors routinely overstate cash flow by forgetting vacancy and capital reserves; this tool bakes those in so your projection survives contact with reality. Adjust the inputs to stress-test a deal and find the rent or purchase price at which it finally turns cash-flow positive.
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Results update live as you type. Estimates only — not financial, tax, or investment advice.
The Formula
Monthly Cash Flow = Effective Rental Income − (Mortgage + Operating Expenses)
Understanding the Rental Property Cash Flow Calculator
Cash flow is what separates a rental that builds wealth from one that slowly drains your savings. This calculator gives you an honest figure by discounting gross rent for vacancy before subtracting the mortgage and operating expenses — because a property is never rented 100% of the time. The most common beginner mistake is treating rent minus mortgage as 'cash flow' while ignoring taxes, insurance, management, repairs, and the capital reserves you must set aside for the roof and HVAC that will eventually fail.
A widely used sanity check is the 50% rule, which assumes that over the long run roughly half of gross rent is consumed by operating expenses, excluding the mortgage. If your expense estimate falls far below that, revisit your assumptions. Many investors also set a minimum cash-flow target — often around $100–$200 per unit per month — to ensure the property has enough buffer to weather turnover and unexpected repairs without going negative.
Frequently Asked Questions
What is good monthly cash flow for a rental property?
A common rule of thumb is a minimum of $100–$200 in cash flow per unit per month after all expenses and reserves. The right target varies by market: cash-flow markets can exceed this easily, while pricey appreciation markets often deliver thin or even slightly negative cash flow that investors accept for equity growth.
What is the 50% rule in real estate?
The 50% rule estimates that, over time, operating expenses (excluding the mortgage) will consume about half of a rental's gross income — covering taxes, insurance, management, maintenance, vacancy, and reserves. It is a quick screening heuristic, not a substitute for itemizing the real expenses on a specific property.
Why should I include vacancy in cash flow calculations?
Because no rental stays occupied permanently. Tenants move out, and units sit empty during turnover and re-leasing. Building in a vacancy allowance of typically 5–10% produces a realistic cash-flow projection instead of an optimistic one that assumes rent you will never actually collect every single month.