Monthly Rental Income (Adjusted for Vacancy):$0.00
Monthly Mortgage Payment (P&I):$0.00
Monthly Operating Expenses:$0.00
Monthly Cash Flow:$0.00
NOI (Annual)$0
Cash on Cash ROI0.00%
Cap Rate0.00%
Mastering Rental Property Analysis
Investing in real estate is one of the most reliable ways to build wealth, but it requires precise mathematical analysis to ensure profitability. This Rental Property Cash Flow Calculator is designed to help investors evaluate the viability of a potential deal by breaking down income, expenses, and key return on investment (ROI) metrics.
How to Calculate Rental Cash Flow
Cash flow is the lifeblood of any rental investment. It is the money left over after all expenses—including the mortgage—are paid. The basic formula used in our calculator is:
Many novice investors make the mistake of calculating cash flow by simply subtracting the mortgage from the rent. This is dangerous because it ignores "silent killers" like vacancy, repairs, capital expenditures (CapEx), and property management fees.
Key Metrics Explained
NOI (Net Operating Income): This is your profitability before the mortgage is paid. It is calculated as Effective Gross Income – Operating Expenses. Banks use this number to determine the strength of the asset.
Cash on Cash Return (CoC): This is perhaps the most important metric for investors. It measures the annual cash flow relative to the total cash invested (Down Payment + Closing Costs + Rehab). A CoC of 8-12% is generally considered a solid return in most markets.
Cap Rate (Capitalization Rate): Calculated as NOI / Purchase Price. This metric allows you to compare the profitability of a property assuming you bought it all cash, helping to compare properties across different markets regardless of financing.
Estimating Expenses Accurately
To get the most accurate result from this calculator, ensure your expense estimates are realistic:
Vacancy: Use 5-8% for standard urban markets.
Maintenance/CapEx: Set aside 10-15% of rent for repairs and future roof/HVAC replacements.
Management: Professional property managers typically charge 8-10% of the monthly rent.
Using this tool allows you to "stress test" your investment. Try increasing the interest rate or vacancy rate to see if the property still cash flows positively. A deal that works only under perfect conditions is a risky investment.
function calculateRental() {
// 1. Get Input Values
var purchasePrice = parseFloat(document.getElementById('purchasePrice').value) || 0;
var downPaymentPercent = parseFloat(document.getElementById('downPaymentPercent').value) || 0;
var interestRate = parseFloat(document.getElementById('interestRate').value) || 0;
var loanTermYears = parseFloat(document.getElementById('loanTerm').value) || 30;
var closingCosts = parseFloat(document.getElementById('closingCosts').value) || 0;
var rehabCosts = parseFloat(document.getElementById('rehabCosts').value) || 0;
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 maintenancePercent = parseFloat(document.getElementById('maintenance').value) || 0;
var managementPercent = parseFloat(document.getElementById('managementFee').value) || 0;
// 2. Perform Calculations
// Loan & Investment
var downPaymentAmount = purchasePrice * (downPaymentPercent / 100);
var loanAmount = purchasePrice – downPaymentAmount;
var totalCashInvested = downPaymentAmount + closingCosts + rehabCosts;
// Mortgage Payment (Monthly P&I)
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = loanTermYears * 12;
var mortgagePayment = 0;
if (monthlyRate > 0) {
mortgagePayment = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
} else {
mortgagePayment = loanAmount / numberOfPayments;
}
// Income
var vacancyAmount = monthlyRent * (vacancyRate / 100);
var effectiveGrossIncome = monthlyRent – vacancyAmount;
// Expenses
var monthlyTax = annualTax / 12;
var monthlyInsurance = annualInsurance / 12;
var monthlyMaintenance = monthlyRent * (maintenancePercent / 100);
var monthlyManagement = monthlyRent * (managementPercent / 100);
var totalMonthlyExpenses = monthlyTax + monthlyInsurance + monthlyMaintenance + monthlyManagement;
// Net Operating Income (NOI)
var monthlyNOI = effectiveGrossIncome – totalMonthlyExpenses;
var annualNOI = monthlyNOI * 12;
// Cash Flow
var monthlyCashFlow = monthlyNOI – mortgagePayment;
var annualCashFlow = monthlyCashFlow * 12;
// ROI Metrics
var cashOnCash = 0;
if (totalCashInvested > 0) {
cashOnCash = (annualCashFlow / totalCashInvested) * 100;
}
var capRate = 0;
if (purchasePrice > 0) {
capRate = (annualNOI / purchasePrice) * 100;
}
// 3. Update DOM
// Helper for currency formatting
function formatMoney(num) {
return '$' + num.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
}
function formatPercent(num) {
return num.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2}) + '%';
}
document.getElementById('resEffectiveIncome').innerText = formatMoney(effectiveGrossIncome);
document.getElementById('resMortgage').innerText = formatMoney(mortgagePayment);
document.getElementById('resExpenses').innerText = formatMoney(totalMonthlyExpenses);
var cfElement = document.getElementById('resCashFlow');
cfElement.innerText = formatMoney(monthlyCashFlow);
if(monthlyCashFlow >= 0) {
cfElement.className = 'rp-positive';
} else {
cfElement.className = 'rp-negative';
}
document.getElementById('resNOI').innerText = formatMoney(annualNOI);
var cocElement = document.getElementById('resCoC');
cocElement.innerText = formatPercent(cashOnCash);
cocElement.className = (cashOnCash >= 0) ? 'rp-positive' : 'rp-negative';
document.getElementById('resCapRate').innerText = formatPercent(capRate);
// Show results
document.getElementById('rpResults').style.display = 'block';
}