function calculateRentalROI() {
// Get Input Values
var price = parseFloat(document.getElementById('rpcPrice').value);
var downPct = parseFloat(document.getElementById('rpcDownPct').value);
var rate = parseFloat(document.getElementById('rpcRate').value);
var term = parseFloat(document.getElementById('rpcTerm').value);
var rent = parseFloat(document.getElementById('rpcRent').value);
var expenses = parseFloat(document.getElementById('rpcExpenses').value);
// Validation
if (isNaN(price) || isNaN(downPct) || isNaN(rate) || isNaN(term) || isNaN(rent) || isNaN(expenses)) {
alert("Please fill in all fields with valid numbers.");
return;
}
// Calculations
var downPaymentAmount = price * (downPct / 100);
var loanAmount = price – downPaymentAmount;
// Mortgage Calculation
var monthlyRate = rate / 100 / 12;
var numPayments = term * 12;
var monthlyMortgage = 0;
if (rate === 0) {
monthlyMortgage = loanAmount / numPayments;
} else {
monthlyMortgage = (loanAmount * monthlyRate) / (1 – Math.pow(1 + monthlyRate, -numPayments));
}
// NOI Calculations
var monthlyNOI = rent – expenses;
var annualNOI = monthlyNOI * 12;
// Cash Flow Calculations
var monthlyCashFlow = monthlyNOI – monthlyMortgage;
var annualCashFlow = monthlyCashFlow * 12;
// Returns Calculations
var capRate = (annualNOI / price) * 100;
var cocReturn = (annualCashFlow / downPaymentAmount) * 100;
// Formatting
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
// Update DOM
document.getElementById('resMonthlyCashFlow').innerHTML = formatter.format(monthlyCashFlow);
document.getElementById('resAnnualCashFlow').innerHTML = formatter.format(annualCashFlow);
document.getElementById('resMortgage').innerHTML = formatter.format(monthlyMortgage);
document.getElementById('resNOI').innerHTML = formatter.format(annualNOI);
document.getElementById('resCoC').innerHTML = cocReturn.toFixed(2) + '%';
document.getElementById('resCapRate').innerHTML = capRate.toFixed(2) + '%';
// Color Coding
var mcFlowEl = document.getElementById('resMonthlyCashFlow');
if (monthlyCashFlow >= 0) {
mcFlowEl.classList.remove('negative');
mcFlowEl.classList.add('positive');
} else {
mcFlowEl.classList.remove('positive');
mcFlowEl.classList.add('negative');
}
var cocEl = document.getElementById('resCoC');
if (cocReturn >= 0) {
cocEl.classList.remove('negative');
cocEl.classList.add('positive');
} else {
cocEl.classList.remove('positive');
cocEl.classList.add('negative');
}
// Show Results
document.getElementById('rpcResults').style.display = 'block';
}
Understanding Your Rental Property Investment Analysis
Investing in real estate is one of the most reliable ways to build wealth, but it requires precise math to ensure you are buying an asset, not a liability. This Rental Property Cash Flow & ROI Calculator helps investors analyze the potential profitability of a residential or commercial rental property by breaking down the key financial metrics.
What is Cash Flow in Real Estate?
Cash flow is the net amount of cash moving into or out of your investment each month. It is calculated by taking your total monthly rental income and subtracting all expenses, including the mortgage payment.
Positive Cash Flow: You are making profit every month after bills are paid.
Negative Cash Flow: The property costs you money to hold every month.
Successful investors typically aim for positive cash flow to create passive income streams and buffer against vacancies or unexpected repairs.
Key Metrics Explained: Cap Rate vs. Cash on Cash Return
While cash flow measures raw dollars, efficiency metrics help you compare different investment opportunities.
Capitalization Rate (Cap Rate)
The Cap Rate measures the natural rate of return of the property assuming you bought it in cash. It is calculated as Net Operating Income (NOI) / Purchase Price. It helps you judge the quality of the deal regardless of financing. A higher Cap Rate generally indicates a better return, though often comes with higher risk.
Cash on Cash Return (CoC ROI)
Cash on Cash Return measures the return on the actual cash you invested (your down payment). It is calculated as Annual Cash Flow / Total Cash Invested. This is often the most important metric for investors using leverage (mortgages), as it shows how hard your specific dollars are working for you.
How to Estimate Expenses
A common mistake for new investors is underestimating expenses. When using this calculator, ensure your "Monthly Expenses" input includes:
Property Taxes: usually 1-2% of property value annually.
Insurance: Fire and hazard insurance premiums.
Maintenance & Repairs: Budget 5-10% of rent for future repairs.
Vacancy: Budget 5-8% of rent for times the unit is empty.
Property Management: Usually 8-10% of rent if you hire a pro.
HOA Fees: If applicable.
Interpreting Your Results
If your Cash on Cash ROI is between 8% and 12%, most investors consider this a solid return, comparable to the stock market but with the added benefits of tax deductions and property appreciation. If your calculation shows a negative cash flow, you may need to negotiate a lower purchase price, increase the down payment to lower the mortgage, or look for a different property.