Analyze the profitability of your real estate investment.
Loan Amount:
Monthly Mortgage (P&I):
Total Monthly Expenses:
Net Operating Income (NOI) / Mo:
Monthly Cash Flow:
Cash-on-Cash ROI:
function calculateCashFlow() {
// Get Input Values
var price = parseFloat(document.getElementById('purchasePrice').value);
var downPercent = parseFloat(document.getElementById('downPayment').value);
var interestRate = parseFloat(document.getElementById('interestRate').value);
var years = parseFloat(document.getElementById('loanTerm').value);
var rent = parseFloat(document.getElementById('monthlyRent').value);
var vacancyPercent = parseFloat(document.getElementById('vacancyRate').value);
var annualTax = parseFloat(document.getElementById('annualTax').value);
var annualIns = parseFloat(document.getElementById('annualInsurance').value);
var hoa = parseFloat(document.getElementById('monthlyHOA').value);
var maintPercent = parseFloat(document.getElementById('maintenance').value);
// Validation
if (isNaN(price) || isNaN(rent)) {
alert("Please enter valid numbers for Purchase Price and Rent.");
return;
}
// Calculations
var downAmount = price * (downPercent / 100);
var loanAmount = price – downAmount;
// Mortgage Calculation
var mortgage = 0;
if (loanAmount > 0 && interestRate > 0) {
var r = interestRate / 100 / 12;
var n = years * 12;
mortgage = loanAmount * (r * Math.pow(1 + r, n)) / (Math.pow(1 + r, n) – 1);
} else if (loanAmount > 0 && interestRate === 0) {
mortgage = loanAmount / (years * 12);
}
// Operating Expenses
var monthlyTax = annualTax / 12;
var monthlyIns = annualIns / 12;
var vacancyCost = rent * (vacancyPercent / 100);
var maintCost = rent * (maintPercent / 100);
// Total Monthly Outflow
var totalOperatingExpenses = monthlyTax + monthlyIns + hoa + maintCost + vacancyCost;
var totalExpenses = totalOperatingExpenses + mortgage;
// Cash Flow
var monthlyCashFlow = rent – totalExpenses;
var annualCashFlow = monthlyCashFlow * 12;
// NOI (Net Operating Income) = Income – Operating Expenses (excluding mortgage)
var monthlyNOI = rent – totalOperatingExpenses;
// ROI (Cash on Cash)
// Note: For simplicity, assuming closing costs are included in down payment or negligible in this basic calc
// A more advanced calc would add ~3% closing costs to the denominator
var roi = 0;
if (downAmount > 0) {
roi = (annualCashFlow / downAmount) * 100;
}
// Formatting Output
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
// Update DOM
document.getElementById('resLoanAmount').innerHTML = formatter.format(loanAmount);
document.getElementById('resMortgage').innerHTML = formatter.format(mortgage);
document.getElementById('resTotalExpenses').innerHTML = formatter.format(totalExpenses);
document.getElementById('resNOI').innerHTML = formatter.format(monthlyNOI);
var cfElement = document.getElementById('resCashFlow');
cfElement.innerHTML = formatter.format(monthlyCashFlow);
if (monthlyCashFlow >= 0) {
cfElement.className = "result-value positive-cf";
} else {
cfElement.className = "result-value negative-cf";
}
var roiElement = document.getElementById('resROI');
roiElement.innerHTML = roi.toFixed(2) + "%";
if (roi >= 0) {
roiElement.className = "result-value positive-cf";
} else {
roiElement.className = "result-value negative-cf";
}
// Show Results
document.getElementById('results').style.display = 'block';
}
Understanding Real Estate Investment Analysis
Investing in rental properties is one of the most reliable ways to build long-term wealth. However, the difference between a successful investment and a financial burden often comes down to the numbers. Using a Rental Property Cash Flow Calculator is an essential step for any investor, whether you are analyzing your first deal or managing a growing portfolio.
This tool helps you determine the viability of a potential purchase by breaking down income, operating expenses, and debt service to reveal the true monthly profit.
How to Calculate Rental Property Cash Flow
Cash flow is the net amount of cash moving into or out of an investment. In real estate, it is calculated using a simple formula:
Gross Income: The total rent collected plus any other income (parking, laundry, etc.).
Operating Expenses: Costs required to run the property, such as taxes, insurance, HOA fees, maintenance, and vacancy allowances.
Net Operating Income (NOI): Gross Income minus Operating Expenses.
Debt Service: Your monthly mortgage payment (Principal and Interest).
Cash Flow: NOI minus Debt Service.
Key Metrics Explained
When analyzing a rental property, two metrics stand out as indicators of success:
1. Cash Flow
This is your "take-home" pay from the property. Positive cash flow means the property pays for itself and generates profit. Negative cash flow means you are paying out of pocket to hold the asset. Most investors aim for at least $100-$300 per door in positive monthly cash flow.
2. Cash-on-Cash ROI
While cash flow is a dollar amount, Cash-on-Cash Return on Investment (ROI) is a percentage that tells you how hard your money is working. It is calculated by dividing your annual pre-tax cash flow by the total cash invested (down payment + closing costs + rehab costs). A generally accepted "good" Cash-on-Cash ROI is between 8% and 12%, though this varies by market strategy.
Why Include Vacancy and Maintenance?
Novice investors often make the mistake of calculating returns based on 100% occupancy and zero repairs. This is unrealistic. Our calculator includes fields for:
Vacancy Rate: Properties will not be rented 365 days a year. A standard 5% vacancy rate accounts for turnover time between tenants.
Maintenance Reserves: Things break. Setting aside 10-15% of the monthly rent ensures you have funds ready for plumbing issues, roof repairs, or painting without disrupting your personal finances.
Conclusion
Before signing a contract, ensure you have run the numbers conservatively. Overestimating rent or underestimating expenses can lead to poor investment performance. Use this calculator to stress-test your deals, adjusting the interest rate or purchase price to see how they impact your bottom line.