Analyze your real estate investment returns instantly
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Investment Analysis
Monthly Cash Flow
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Cash on Cash Return
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Cap Rate
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Monthly Mortgage
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function calculateROI() {
// 1. Get Inputs
var price = parseFloat(document.getElementById('purchasePrice').value);
var downPercent = parseFloat(document.getElementById('downPaymentPercent').value);
var rate = parseFloat(document.getElementById('interestRate').value);
var years = parseFloat(document.getElementById('loanTerm').value);
var income = parseFloat(document.getElementById('rentalIncome').value);
var tax = parseFloat(document.getElementById('propertyTax').value);
var ins = parseFloat(document.getElementById('insurance').value);
var maint = parseFloat(document.getElementById('maintenance').value);
// Validation
if (isNaN(price) || isNaN(downPercent) || isNaN(rate) || isNaN(years) ||
isNaN(income) || isNaN(tax) || isNaN(ins) || isNaN(maint)) {
alert("Please fill in all fields with valid numbers.");
return;
}
// 2. Loan Calculations
var downPaymentAmount = price * (downPercent / 100);
var loanAmount = price – downPaymentAmount;
// Monthly Interest Rate
var monthlyRate = (rate / 100) / 12;
var totalMonths = years * 12;
// Mortgage Payment Calculation (Principal + Interest)
var mortgagePayment = 0;
if (rate === 0) {
mortgagePayment = loanAmount / totalMonths;
} else {
mortgagePayment = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, totalMonths)) / (Math.pow(1 + monthlyRate, totalMonths) – 1);
}
// 3. Expense Calculations
var totalMonthlyExpenses = mortgagePayment + tax + ins + maint;
var operatingExpenses = tax + ins + maint; // Expenses excluding mortgage for Cap Rate
// 4. Return Calculations
var monthlyCashFlow = income – totalMonthlyExpenses;
var annualCashFlow = monthlyCashFlow * 12;
var annualNOI = (income – operatingExpenses) * 12; // Net Operating Income
// Cash on Cash Return = Annual Pre-Tax Cash Flow / Total Cash Invested
// Assuming Closing Costs are roughly 2% of price for simplicity in this model,
// or we can stick to just Down Payment if we want a stricter definition.
// Let's use Down Payment to be consistent with the inputs provided.
var totalCashInvested = downPaymentAmount;
var cocReturn = 0;
if (totalCashInvested > 0) {
cocReturn = (annualCashFlow / totalCashInvested) * 100;
}
// Cap Rate = Annual NOI / Current Market Value (Purchase Price)
var capRate = (annualNOI / price) * 100;
// 5. Update UI
var resCashFlow = document.getElementById('resCashFlow');
var resCoC = document.getElementById('resCoC');
var resCapRate = document.getElementById('resCapRate');
var resMortgage = document.getElementById('resMortgage');
// Formatting currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
});
resMortgage.innerText = formatter.format(mortgagePayment);
resCashFlow.innerText = formatter.format(monthlyCashFlow);
resCoC.innerText = cocReturn.toFixed(2) + "%";
resCapRate.innerText = capRate.toFixed(2) + "%";
// Color coding for Cash Flow
if (monthlyCashFlow >= 0) {
resCashFlow.className = "result-value positive";
} else {
resCashFlow.className = "result-value negative";
}
// Show results
document.getElementById('resultsSection').style.display = 'block';
}
Understanding Rental Property Cash Flow Analysis
Investing in real estate is one of the most reliable ways to build wealth, but simply buying a property doesn't guarantee profit. The key to successful real estate investing lies in the numbers. This Rental Property Cash Flow Calculator helps you determine if a potential property is a sound financial investment by analyzing key metrics like monthly cash flow, Cash on Cash Return, and Cap Rate.
What is Monthly Cash Flow?
Monthly cash flow is the net amount of money left in your pocket after all expenses are paid. It is calculated by taking your total monthly rental income and subtracting all operating expenses and debt service (mortgage payments). A positive cash flow indicates the property is generating income, while a negative cash flow means the property costs you money to hold every month.
Two of the most important metrics for evaluating rental properties are Cash on Cash Return and Cap Rate. While they may seem similar, they measure different aspects of the investment.
Cash on Cash Return (CoC): This measures the return on the actual cash you invested (down payment). It gives you a clear picture of how hard your money is working for you compared to other investments like the stock market. A generally accepted "good" CoC return is often considered to be between 8% and 12%.
Cap Rate (Capitalization Rate): This measures the property's natural rate of return assuming you paid all cash. It helps compare properties regardless of financing. It is calculated by dividing the Net Operating Income (NOI) by the property's value.
Why Accurate Expense Estimation Matters
One of the biggest mistakes new investors make is underestimating expenses. When using the calculator above, be sure to include not just the mortgage, but also property taxes, insurance premiums, HOA fees, and a buffer for maintenance and vacancies. A common rule of thumb is to set aside 10-15% of the rent for repairs and vacancy to ensure your cash flow projection remains realistic over the long term.