function calculateRentalROI() {
// Get Input Values
var price = parseFloat(document.getElementById('purchasePrice').value) || 0;
var closing = parseFloat(document.getElementById('closingCosts').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) || 30;
var monthlyRent = parseFloat(document.getElementById('monthlyRent').value) || 0;
var vacancyRate = parseFloat(document.getElementById('vacancyRate').value) || 0;
var annualTax = parseFloat(document.getElementById('propertyTax').value) || 0;
var annualInsurance = parseFloat(document.getElementById('insurance').value) || 0;
var monthlyMaint = parseFloat(document.getElementById('maintenance').value) || 0;
var monthlyOther = parseFloat(document.getElementById('otherExpenses').value) || 0;
// Calculations
// 1. Initial Investment
var downPaymentAmount = price * (downPercent / 100);
var loanAmount = price – downPaymentAmount;
var totalInitialInvestment = downPaymentAmount + closing;
// 2. Mortgage Payment
var monthlyMortgage = 0;
if (loanAmount > 0) {
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = years * 12;
if (monthlyRate === 0) {
monthlyMortgage = loanAmount / numberOfPayments;
} else {
monthlyMortgage = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
}
}
// 3. Operating Expenses (Monthly)
var monthlyTax = annualTax / 12;
var monthlyInsurance = annualInsurance / 12;
var totalOperatingExpenses = monthlyTax + monthlyInsurance + monthlyMaint + monthlyOther;
// 4. Income
var vacancyLoss = monthlyRent * (vacancyRate / 100);
var effectiveGrossIncome = monthlyRent – vacancyLoss;
// 5. Net Operating Income (NOI) = Income – Operating Expenses (No Mortgage)
var monthlyNOI = effectiveGrossIncome – totalOperatingExpenses;
var annualNOI = monthlyNOI * 12;
// 6. Cash Flow = NOI – Mortgage
var totalMonthlyExpenses = totalOperatingExpenses + monthlyMortgage;
var monthlyCashFlow = effectiveGrossIncome – totalMonthlyExpenses;
var annualCashFlow = monthlyCashFlow * 12;
// 7. Metrics
var capRate = (price > 0) ? (annualNOI / price) * 100 : 0;
var cashOnCash = (totalInitialInvestment > 0) ? (annualCashFlow / totalInitialInvestment) * 100 : 0;
// Display Results
document.getElementById('rpc-results-area').style.display = 'block';
var mcfEl = document.getElementById('monthlyCashFlow');
mcfEl.textContent = formatCurrency(monthlyCashFlow);
mcfEl.className = monthlyCashFlow >= 0 ? 'rpc-result-value rpc-highlight rpc-positive' : 'rpc-result-value rpc-highlight rpc-negative';
var acfEl = document.getElementById('annualCashFlow');
acfEl.textContent = formatCurrency(annualCashFlow);
acfEl.className = annualCashFlow >= 0 ? 'rpc-result-value rpc-positive' : 'rpc-result-value rpc-negative';
var cocEl = document.getElementById('cashOnCash');
cocEl.textContent = cashOnCash.toFixed(2) + "%";
cocEl.className = cashOnCash >= 0 ? 'rpc-result-value rpc-highlight rpc-positive' : 'rpc-result-value rpc-highlight rpc-negative';
document.getElementById('capRate').textContent = capRate.toFixed(2) + "%";
document.getElementById('totalExpenses').textContent = formatCurrency(totalMonthlyExpenses);
document.getElementById('noiMonthly').textContent = formatCurrency(monthlyNOI);
document.getElementById('totalInvestment').textContent = formatCurrency(totalInitialInvestment);
}
function formatCurrency(num) {
return "$" + num.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}
Understanding Your Rental Property Analysis
Investing in real estate is a numbers game. To ensure a profitable investment, you need to accurately calculate your potential returns before signing on the dotted line. This Rental Property Cash Flow Calculator is designed to help real estate investors analyze the profitability of a potential rental property purchase.
Key Metrics Explained
1. Cash Flow
Cash Flow is the net amount of cash moving in or out of the investment each month. It is calculated by subtracting all expenses (mortgage, taxes, insurance, maintenance, vacancy reserves) from the gross rental income. Positive cash flow means the property is generating profit month-over-month, while negative cash flow means you are losing money to hold the property.
2. Cash on Cash Return (CoC ROI)
The Cash on Cash Return measures the annual return on the actual cash you invested, rather than the total purchase price. This is one of the most important metrics for investors because it reflects the efficiency of your capital.
A "good" CoC return varies by market and strategy, but many investors aim for 8-12% or higher.
3. Cap Rate (Capitalization Rate)
The Cap Rate helps compare the profitability of different properties regardless of how they are financed. It assumes you bought the property with 100% cash.
Formula: Net Operating Income (NOI) / Purchase Price
Unlike Cash on Cash return, the Cap Rate does not deduct mortgage payments. It strictly measures the property's ability to generate operating income relative to its price.
4. Net Operating Income (NOI)
NOI is the total income the property generates after all operating expenses (vacancy, taxes, maintenance, management) are paid, but before debt service (mortgage payments) and income taxes. This figure is crucial for lenders when determining if a property covers its debt obligations.
Factors Affecting Profitability
Vacancy Rate: Never assume 100% occupancy. A standard vacancy rate to estimate is 5% to 8%, accounting for tenant turnover.
Maintenance Reserves: Things break. Setting aside 10-15% of rent for repairs ensures your cash flow calculations are realistic over the long term.
Leverage: Using a mortgage (leverage) can significantly boost your Cash on Cash return, but it also increases risk if the property sits vacant.
Use this calculator to adjust variables like purchase price, rent, and down payment to find the "sweet spot" where your investment meets your financial goals.