Calculating the potential cash flow of a rental property is the single most important step in real estate investing. This calculator allows you to analyze a potential investment by factoring in purchase costs, financing, rental income, and detailed expenses.
Purchase Info
Financing
Income & Expenses
Total Initial Cash Needed:
Monthly Mortgage Payment (P&I):
Total Monthly Expenses:
Net Operating Income (NOI):
Monthly Cash Flow:
Cash on Cash Return (ROI):
function calculateCashFlow() {
// Get Input Values
var price = parseFloat(document.getElementById('purchasePrice').value) || 0;
var closing = parseFloat(document.getElementById('closingCosts').value) || 0;
var rehab = parseFloat(document.getElementById('rehabCosts').value) || 0;
var downPercent = parseFloat(document.getElementById('downPaymentPercent').value) || 0;
var interestRate = parseFloat(document.getElementById('interestRate').value) || 0;
var years = parseFloat(document.getElementById('loanTerm').value) || 0;
var rent = parseFloat(document.getElementById('monthlyRent').value) || 0;
var annualTax = parseFloat(document.getElementById('propertyTax').value) || 0;
var annualIns = parseFloat(document.getElementById('insurance').value) || 0;
var hoa = parseFloat(document.getElementById('hoa').value) || 0;
var vacancyPercent = parseFloat(document.getElementById('vacancyRate').value) || 0;
var maintenancePercent = parseFloat(document.getElementById('maintenanceRate').value) || 0;
// Calculations
// 1. Initial Investment
var downPaymentAmount = price * (downPercent / 100);
var loanAmount = price – downPaymentAmount;
var totalCashNeeded = downPaymentAmount + closing + rehab;
// 2. Mortgage Payment (Monthly P&I)
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = years * 12;
var mortgagePayment = 0;
if (interestRate > 0) {
mortgagePayment = loanAmount * monthlyRate * (Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
} else {
mortgagePayment = loanAmount / numberOfPayments;
}
// 3. Operating Expenses
var monthlyTax = annualTax / 12;
var monthlyIns = annualIns / 12;
var vacancyCost = rent * (vacancyPercent / 100);
var maintenanceCost = rent * (maintenancePercent / 100);
var totalOperatingExpenses = monthlyTax + monthlyIns + hoa + vacancyCost + maintenanceCost;
var totalMonthlyExpenses = totalOperatingExpenses + mortgagePayment;
// 4. Returns
var noi = rent – totalOperatingExpenses; // Net Operating Income
var monthlyCashFlow = rent – totalMonthlyExpenses;
var annualCashFlow = monthlyCashFlow * 12;
var cocReturn = 0;
if (totalCashNeeded > 0) {
cocReturn = (annualCashFlow / totalCashNeeded) * 100;
}
// Display Results
document.getElementById('results-area').style.display = 'block';
document.getElementById('displayTotalCash').innerText = '$' + totalCashNeeded.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('displayMortgage').innerText = '$' + mortgagePayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('displayExpenses').innerText = '$' + totalMonthlyExpenses.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('displayNOI').innerText = '$' + noi.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + ' / mo';
var cashFlowElem = document.getElementById('displayMonthlyCashFlow');
cashFlowElem.innerText = '$' + monthlyCashFlow.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
// Visual feedback for negative cash flow
if (monthlyCashFlow < 0) {
cashFlowElem.classList.add('negative-result');
cashFlowElem.classList.remove('highlight-result');
} else {
cashFlowElem.classList.remove('negative-result');
cashFlowElem.classList.add('highlight-result');
}
var cocElem = document.getElementById('displayCOC');
cocElem.innerText = cocReturn.toFixed(2) + '%';
if (cocReturn < 0) {
cocElem.classList.add('negative-result');
cocElem.classList.remove('highlight-result');
} else {
cocElem.classList.remove('negative-result');
cocElem.classList.add('highlight-result');
}
}
Understanding Rental Property Cash Flow
In real estate investing, "Cash Flow" refers to the net income generated by a property after all expenses and mortgage payments have been deducted from the rental income. It is the lifeblood of a rental business and determines whether an asset is a liability or a profit generator.
How to Use This Calculator
To get the most accurate results from our Rental Property Calculator, ensure you have the following data points:
Purchase Price: The agreed-upon price of the property.
Financing Details: Your down payment percentage, interest rate, and loan term (usually 15 or 30 years).
Operating Expenses: These are often overlooked by beginners. Be sure to account for Vacancy (typically 5-10%), Maintenance (saving for future repairs), Taxes, and Insurance.
What is a Good Cash on Cash Return?
Cash on Cash (CoC) Return measures the annual return on the actual cash you invested, rather than the total loan amount. While "good" is subjective, many investors aim for:
8-12%: Solid return for average markets.
15%+: Excellent return, often found in high-cash-flow markets or through value-add strategies (renovations).
Negative Return: This indicates the property costs you money to hold every month. This is generally avoided unless the property is expected to appreciate significantly in value.
Common Mistakes to Avoid
New investors often underestimate Maintenance and Vacancy. A heater will eventually break, and a tenant will eventually move out. Setting aside a percentage of monthly rent (e.g., 10% for maintenance and 5% for vacancy) ensures you have the cash reserves when these events occur, preventing your investment from becoming a financial burden.