Analyze cash flow, cap rate, and ROI for your real estate investment.
Purchase Info
Loan Details
Income & Expenses
Monthly Analysis
Monthly Cash Flow
$0.00
Mortgage (P&I)
$0.00
Total Monthly Expenses
$0.00
Annual Returns
Cash-on-Cash ROI
0.00%
Cap Rate
0.00%
Net Operating Income
$0.00
function calculateRental() {
// Get Inputs
var price = parseFloat(document.getElementById('rpc_price').value);
var downPercent = parseFloat(document.getElementById('rpc_down').value);
var closingCosts = parseFloat(document.getElementById('rpc_closing').value);
var interestRate = parseFloat(document.getElementById('rpc_rate').value);
var termYears = parseFloat(document.getElementById('rpc_term').value);
var monthlyRent = parseFloat(document.getElementById('rpc_rent').value);
var annualTax = parseFloat(document.getElementById('rpc_tax').value);
var annualIns = parseFloat(document.getElementById('rpc_insurance').value);
var monthlyHoa = parseFloat(document.getElementById('rpc_hoa').value);
var maintPercent = parseFloat(document.getElementById('rpc_maint').value);
// Validation
if (isNaN(price) || isNaN(downPercent) || isNaN(interestRate) || isNaN(monthlyRent)) {
alert("Please enter valid numbers for Price, Down Payment, Rate, and Rent.");
return;
}
// 1. Loan Calculation
var downPaymentAmount = price * (downPercent / 100);
var loanAmount = price – downPaymentAmount;
var monthlyRate = interestRate / 100 / 12;
var numberOfPayments = termYears * 12;
var monthlyMortgage = 0;
if (interestRate > 0) {
monthlyMortgage = (loanAmount * monthlyRate) / (1 – Math.pow(1 + monthlyRate, -numberOfPayments));
} else {
monthlyMortgage = loanAmount / numberOfPayments;
}
// 2. Expenses Calculation
var monthlyTax = annualTax / 12;
var monthlyIns = annualIns / 12;
var monthlyMaintVacancy = monthlyRent * (maintPercent / 100);
var totalMonthlyExpenses = monthlyMortgage + monthlyTax + monthlyIns + monthlyHoa + monthlyMaintVacancy;
// 3. Profit/Loss Calculation
var monthlyCashFlow = monthlyRent – totalMonthlyExpenses;
var annualCashFlow = monthlyCashFlow * 12;
// 4. NOI Calculation (Income – Expenses excluding Mortgage)
var monthlyOperatingExpenses = monthlyTax + monthlyIns + monthlyHoa + monthlyMaintVacancy;
var annualNOI = (monthlyRent * 12) – (monthlyOperatingExpenses * 12);
// 5. ROI Metrics
var totalCashInvested = downPaymentAmount + closingCosts;
var cashOnCashROI = 0;
if (totalCashInvested > 0) {
cashOnCashROI = (annualCashFlow / totalCashInvested) * 100;
}
var capRate = 0;
if (price > 0) {
capRate = (annualNOI / price) * 100;
}
// Display Results
document.getElementById('rpc_results').style.display = 'block';
// Format Currency Helper
var fmtMoney = new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' });
document.getElementById('rpc_out_mortgage').innerText = fmtMoney.format(monthlyMortgage);
document.getElementById('rpc_out_total_exp').innerText = fmtMoney.format(totalMonthlyExpenses);
var cfEl = document.getElementById('rpc_out_cashflow');
cfEl.innerText = fmtMoney.format(monthlyCashFlow);
cfEl.className = 'rpc-result-value ' + (monthlyCashFlow >= 0 ? 'rpc-value-positive' : 'rpc-value-negative');
document.getElementById('rpc_out_noi').innerText = fmtMoney.format(annualNOI);
var cocEl = document.getElementById('rpc_out_coc');
cocEl.innerText = cashOnCashROI.toFixed(2) + "%";
cocEl.className = 'rpc-result-value ' + (cashOnCashROI >= 0 ? 'rpc-value-positive' : 'rpc-value-negative');
document.getElementById('rpc_out_cap').innerText = capRate.toFixed(2) + "%";
}
How to Use This Rental Property Calculator
Investing in real estate is one of the most reliable ways to build wealth, but it requires precise math. This Rental Property Cash Flow Calculator helps investors determine if a specific property will generate profit (positive cash flow) or cost money to hold (negative cash flow).
Understanding Key Metrics
1. Monthly Cash Flow
This is the most critical number for buy-and-hold investors. It represents the money left over after all expenses are paid.
Formula: Total Rental Income – Total Expenses (Mortgage, Taxes, Insurance, HOA, Maintenance).
Goal: Look for positive cash flow (e.g., $200+ per door) to ensure the asset pays for itself.
2. Cash-on-Cash ROI
This metric tells you how hard your actual invested cash is working. Unlike simple ROI, it compares your annual profit to the actual cash you put down (Down Payment + Closing Costs), not the total property price.
Formula: (Annual Cash Flow / Total Cash Invested) × 100
Good Target: Many investors aim for 8-12% or higher, significantly beating average stock market returns.
3. Cap Rate (Capitalization Rate)
The Cap Rate measures a property's natural rate of return assuming you bought it with all cash (no loan). It helps compare the profitability of different properties regardless of financing.
Formula: Net Operating Income (NOI) / Purchase Price
Insight: A higher Cap Rate generally indicates higher risk or higher return potential.
Estimating Expenses Accurately
One of the biggest mistakes new investors make is underestimating expenses. Always include:
Vacancy & Maintenance: Even if the house is new, budget 5-10% of rent for repairs and empty months.
Property Taxes & Insurance: These can vary wildly by location. Check local county assessor sites for accurate tax history.
HOA Fees: If investing in a condo or managed community, these monthly fees eat directly into cash flow.
Use this calculator before making any offer to ensure the numbers support your investment goals.