Please check your inputs. Ensure all values are positive numbers.
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Monthly Cash Flow
Cash on Cash Return
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Cap Rate
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Monthly NOI
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Monthly Expenses
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Mortgage Payment
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Total Investment
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Understanding Rental Property Cash Flow
Cash flow is the lifeblood of any rental property investment. It represents the net amount of money moving into or out of your business every month after all expenses and debt service (mortgage) have been paid. A positive cash flow ensures that the property pays for itself and generates income, while negative cash flow means you are losing money every month to hold the asset.
Key Metrics Explained
Cash Flow: The final profit after all bills. Calculated as Total Income – Total Expenses – Mortgage Payment.
NOI (Net Operating Income): The profitability of the property excluding financing costs. It is calculated as Total Income – Operating Expenses. Banks use this to judge the property's standalone profitability.
Cash on Cash Return (CoC): A percentage that measures the annual return on the actual cash you invested (Down Payment + Closing Costs). It's a critical metric for comparing real estate against other investment vehicles like stocks.
Cap Rate (Capitalization Rate): Calculated as Annual NOI / Purchase Price. This measures the natural rate of return of the property assuming you bought it with all cash. It helps compare properties in different markets regardless of how they are financed.
How to Analyze the Results
When using this Rental Property Cash Flow Calculator, aim for a positive monthly cash flow that acts as a buffer against unexpected repairs or vacancies. Many investors look for the "1% Rule" (monthly rent should be 1% of the purchase price) as a quick filter, but a detailed analysis of Expenses, Vacancy Rates (typically 5-8%), and Maintenance reserves (typically 5-10%) provides the true picture of an investment's viability.
Estimating Expenses
One of the biggest mistakes new investors make is underestimating expenses. Always account for:
Vacancy: You won't have a tenant 12 months a year forever. Set aside 5-10% of rent.
CapEx (Capital Expenditures): Roofs, HVACs, and water heaters eventually break. Allocating a percentage of monthly rent to a reserve fund is essential for long-term solvency.
Property Management: Even if you self-manage now, budgeting 8-10% for management ensures the deal still works if you hire a professional later.
function calculateRentalCashFlow() {
// 1. Get Input Values
var price = parseFloat(document.getElementById('purchasePrice').value);
var down = parseFloat(document.getElementById('downPayment').value);
var rate = parseFloat(document.getElementById('interestRate').value);
var years = parseFloat(document.getElementById('loanTerm').value);
var closing = parseFloat(document.getElementById('closingCosts').value);
var rent = parseFloat(document.getElementById('monthlyRent').value);
var taxYear = parseFloat(document.getElementById('propertyTax').value);
var insuranceYear = parseFloat(document.getElementById('insurance').value);
var hoa = parseFloat(document.getElementById('hoaFees').value);
var vacancyPct = parseFloat(document.getElementById('vacancyRate').value);
var maintPct = parseFloat(document.getElementById('maintenanceRate').value);
// 2. Validate Inputs
if (isNaN(price) || isNaN(down) || isNaN(rent) || price < 0 || rent 0) {
if (rate === 0) {
mortgage = loanAmount / totalPayments;
} else {
mortgage = (loanAmount * monthlyRate * Math.pow(1 + monthlyRate, totalPayments)) / (Math.pow(1 + monthlyRate, totalPayments) – 1);
}
}
// 4. Monthly Expense Calculations
var monthlyTax = taxYear / 12;
var monthlyInsurance = insuranceYear / 12;
var vacancyCost = rent * (vacancyPct / 100);
var maintCost = rent * (maintPct / 100);
var operatingExpenses = monthlyTax + monthlyInsurance + hoa + vacancyCost + maintCost;
var totalExpensesMonthly = operatingExpenses + mortgage;
// 5. Income & Profit Calculations
var effectiveGrossIncome = rent; // Usually vacancy is treated as an expense, but logically it reduces income. Here we treat as expense for line-item clarity, or we can subtract. Let's stick to standard NOI formula: NOI = Income – Operating Expenses.
// Note: Some models subtract vacancy from Income first. Here we included vacancy in 'operatingExpenses' list for visualization.
var monthlyNOI = rent – operatingExpenses;
var monthlyCashFlow = monthlyNOI – mortgage;
var annualCashFlow = monthlyCashFlow * 12;
var annualNOI = monthlyNOI * 12;
// 6. Return Metrics
var totalInvested = down + closing;
var coc = 0;
if (totalInvested > 0) {
coc = (annualCashFlow / totalInvested) * 100;
}
var capRate = 0;
if (price > 0) {
capRate = (annualNOI / price) * 100;
}
// 7. Display Results
var currencyFormatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
var percentFormatter = new Intl.NumberFormat('en-US', {
style: 'decimal',
minimumFractionDigits: 2,
maximumFractionDigits: 2
});
document.getElementById('monthlyCashFlow').innerText = currencyFormatter.format(monthlyCashFlow);
document.getElementById('monthlyCashFlow').style.color = monthlyCashFlow >= 0 ? '#2c7744' : '#d63031';
document.getElementById('cocReturn').innerText = percentFormatter.format(coc) + "%";
document.getElementById('capRate').innerText = percentFormatter.format(capRate) + "%";
document.getElementById('monthlyNOI').innerText = currencyFormatter.format(monthlyNOI);
document.getElementById('totalExpenses').innerText = currencyFormatter.format(operatingExpenses); // Displaying OpEx, not including mortgage, for clarity on NOI
document.getElementById('mortgagePayment').innerText = currencyFormatter.format(mortgage);
document.getElementById('totalInvestment').innerText = currencyFormatter.format(totalInvested);
document.getElementById('resultContainer').style.display = 'block';
}