function calculateRental() {
// 1. Get Inputs
var price = parseFloat(document.getElementById('propPrice').value) || 0;
var downPerc = parseFloat(document.getElementById('downPayment').value) || 0;
var rate = parseFloat(document.getElementById('intRate').value) || 0;
var years = parseFloat(document.getElementById('loanTerm').value) || 0;
var rent = parseFloat(document.getElementById('monthlyRent').value) || 0;
var tax = parseFloat(document.getElementById('propTax').value) || 0;
var insurance = parseFloat(document.getElementById('insCost').value) || 0;
var hoa = parseFloat(document.getElementById('hoaCost').value) || 0;
var maintVacPerc = parseFloat(document.getElementById('otherExp').value) || 0;
// 2. Calculate Loan Details
var downAmount = price * (downPerc / 100);
var loanAmount = price – downAmount;
var monthlyRate = rate / 100 / 12;
var totalPayments = years * 12;
var mortgagePayment = 0;
if (monthlyRate > 0) {
mortgagePayment = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, totalPayments)) / (Math.pow(1 + monthlyRate, totalPayments) – 1);
} else {
mortgagePayment = loanAmount / totalPayments;
}
// 3. Calculate Expenses
var monthlyTax = tax / 12;
var monthlyIns = insurance / 12;
var monthlyMaintVac = rent * (maintVacPerc / 100);
// Total Operating Expenses (excluding mortgage)
var totalOpExpenses = monthlyTax + monthlyIns + hoa + monthlyMaintVac;
// Total Monthly Outflow (Operating + Debt Service)
var totalOutflow = totalOpExpenses + mortgagePayment;
// 4. Calculate Key Metrics
var monthlyCashFlow = rent – totalOutflow;
var annualCashFlow = monthlyCashFlow * 12;
// Net Operating Income (NOI) = Annual Income – Annual Operating Expenses (Excl Debt)
var annualNOI = (rent * 12) – (totalOpExpenses * 12);
// Cap Rate = (NOI / Purchase Price) * 100
var capRate = 0;
if (price > 0) {
capRate = (annualNOI / price) * 100;
}
// Cash on Cash Return = (Annual Cash Flow / Total Cash Invested) * 100
// Assuming Cash Invested is just Down Payment for simplicity here
var cocReturn = 0;
if (downAmount > 0) {
cocReturn = (annualCashFlow / downAmount) * 100;
}
// 5. Update UI
var cashFlowEl = document.getElementById('resCashFlow');
cashFlowEl.innerText = '$' + monthlyCashFlow.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
if(monthlyCashFlow < 0) {
cashFlowEl.style.color = '#c0392b';
} else {
cashFlowEl.style.color = '#27ae60';
}
document.getElementById('resCoc').innerText = cocReturn.toFixed(2) + '%';
document.getElementById('resCap').innerText = capRate.toFixed(2) + '%';
document.getElementById('resNoi').innerText = '$' + annualNOI.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resMortgage').innerText = '$' + mortgagePayment.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resExpenses').innerText = '$' + totalOutflow.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('results').style.display = 'block';
}
Maximizing ROI with the Rental Property Cash Flow Calculator
Investing in real estate is one of the most reliable ways to build wealth, but success hinges on the numbers. This Rental Property Cash Flow Calculator helps investors analyze potential deals by breaking down income, expenses, and financing costs to determine the true profitability of a rental unit.
Why Cash Flow Matters
Cash flow is the net amount of money moving in and out of a business. In real estate, positive cash flow means your rental income exceeds your mortgage payments and operating expenses. This is the "passive income" investors seek. Negative cash flow means you are losing money every month to hold the property.
Understanding the Key Metrics
NOI (Net Operating Income): This represents the profitability of the property before leverage (mortgage) is considered. It is calculated by subtracting all operating expenses (taxes, insurance, maintenance) from the total rental income.
Cap Rate (Capitalization Rate): A measure of the property's natural rate of return. It is calculated as NOI / Purchase Price. A higher cap rate generally indicates a better return, though often comes with higher risk.
Cash on Cash Return: This metric tells you how hard your actual invested cash is working. It compares your annual pre-tax cash flow to the total cash invested (down payment + closing costs). This is often considered the most important metric for leverage-focused investors.
How to Estimate Expenses
Many new investors underestimate expenses. Beyond the mortgage, you must account for:
Vacancy: Properties won't be rented 100% of the time. A standard safety margin is 5-8% of gross rent.
Maintenance: Roofs leak and toilets break. Allocating 5-10% of monthly rent for repairs is a prudent strategy.
CapEx (Capital Expenditures): Major replacements like HVAC or flooring.
Frequently Asked Questions
What is a "good" Cash on Cash return?
While this varies by market and strategy, many investors target a Cash on Cash (CoC) return of 8% to 12%. In highly appreciative markets, investors might accept lower cash flow (4-6%) in exchange for future equity gains.
Does this calculator include tax benefits?
This calculator focuses on pre-tax cash flow. Real estate offers significant tax advantages like depreciation, which can offset income, but these should be calculated separately with a CPA.
How does the interest rate affect my cash flow?
Interest rates have a direct impact on your mortgage payment. A 1% increase in interest rates can significantly increase your monthly debt service, potentially turning a positive cash flow deal into a negative one. Always stress-test your numbers with higher rates.