Reserve for vacancy, repairs, management, and capital expenditures. Taxes and insurance vary by market.
Calculation details
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Use this result
Share the current inputs or ask ChatGPT to explain the calculation in context.
What does this calculator estimate?
Cash flow is the actual monthly money a rental property generates after all income and expenses — including the mortgage payment. It is the most directly practical real-estate metric because it answers 'does this property pay me to hold it?'
- Cash flow = income − expenses
- After mortgage (unlike NOI)
- Direct practical 'does it pay itself' metric
What cash flow measures
Cash flow is the rent minus every cost of owning and running the property — the money that actually lands in your account each month. It's the operating pulse of buy-and-hold investing: positive flow pays you while you wait for appreciation.
Limitations to watch for
The estimate uses your inputs — vacancies, repairs, and capital expenses average higher than owners plan. Maintenance should be budgeted at 1–3% of property value per year. Cash flow ignores tax benefits and principal paydown (the ROI calculator includes them).
How to use it in practice
Enter realistic income (rent minus vacancy allowance) and all costs including a maintenance reserve. If flow is negative, the property is a bet on appreciation alone. Compare candidates on monthly flow per dollar invested.
['Enter monthly rent and other income.', 'Enter the mortgage, taxes, insurance, and maintenance.', 'Read the monthly and annual cash flow.']
What cash flow measures
Cash flow is income minus expenses over a period — for a rental, rent plus other income minus mortgage, taxes, insurance, maintenance, and vacancy. A property that nets $300 monthly produces $3,600 annually. The calculator runs the monthly and annual picture.
Cash flow vs. profit
Cash flow includes principal paydown (a non-cash expense for accounting but a real cash outflow) and excludes appreciation. A property can be cash-flow negative while building equity — the two are different statements. The calculator focuses on cash; equity growth is the partner metric.
The 50 percent rule
A common screen: operating expenses (everything except the mortgage) run about 50 percent of gross rent. $2,000 rent → $1,000 expenses, leaving $1,000 for the mortgage and cash flow. It is a rough filter, not a substitute for line-by-line estimates.
Vacancy and repairs are certainties
Every property has vacant months and repair bills. Budgeting 5–8 percent of rent for vacancy and 10–15 percent for maintenance and capex turns 'profitable on paper' into 'profitable after reality.' The calculator includes these allowances.
A worked example
$2,000 rent, $300 other income, $1,200 mortgage, $300 taxes/insurance, $150 maintenance, $100 vacancy reserve: cash flow = $550 monthly, $6,600 annually. The calculator shows the line items so the number is inspectable.
How this calculator works
Formula
Monthly cash flow = (rent + other income) − (mortgage + taxes/insurance + maintenance + other expenses). Positive flow is the goal of buy-and-hold investing.
Worked example
$1,800 rent + $200 other = $2,000 income; $1,200 mortgage + $300 taxes/insurance + $150 maintenance + $50 misc = $1,700; cash flow = $300/month.
Assumptions to verify
- Rent and expenses are steady monthly values.
- A maintenance reserve is included by the user.
- No vacancy loss is modeled unless entered.
Frequently asked questions
How do I calculate rental cash flow?
Income minus expenses: $2,000 − $1,700 = $300/month.
What counts as income?
Rent plus any other income: laundry, parking, storage, pet fees.
What counts as expenses?
Mortgage, property taxes, insurance, maintenance, property management, utilities, and vacancy.
What is good cash flow?
A common target is 8–12% cash-on-cash return, or $100–300/month per door depending on market.
Why is my flow lower than expected?
Maintenance, vacancies, and management fees are routinely underestimated — budget 1–3% of value for upkeep.
Does cash flow include appreciation?
No — appreciation is unrealized until sale. The ROI calculator combines both.
Is negative cash flow bad?
Sometimes — if you're banking on appreciation or tax benefits, negative flow can still work, but it's riskier.
Is cash flow the same as profit?
No — cash flow counts principal paydown as an outflow and ignores appreciation.
What is the 50% rule?
Operating expenses run about half of gross rent — a rough screening filter.
How much should I reserve for vacancy?
5–8% of rent is a common planning allowance.
Cite this tool
BoringToolsKit. “Real Estate Cash Flow Calculator.” boringtoolskit.com/cash-flow-calculator/ (reviewed 2026-08-25). Free to reference in articles, syllabi, and answer posts with a link.
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