Investing in real estate is one of the most reliable ways to build wealth, but the difference between a successful investment and a financial burden often comes down to one metric: Cash Flow. This calculator is designed specifically for real estate investors to analyze the profitability of a rental property before making a purchase.
Unlike simple mortgage calculators, this tool accounts for the specific operating expenses associated with being a landlord, including vacancy rates, property management, and maintenance reserves. By inputting your purchase details and projected income, you can instantly determine your Net Operating Income (NOI), Cash on Cash Return, and monthly cash flow.
Investment Analyzer
Monthly Cash Flow
$0.00
Cash on Cash Return
0.00%
Cap Rate
0.00%
Monthly Financial Breakdown
Gross Scheduled Rent:$0
– Vacancy Loss:-$0
= Effective Gross Income:$0
– Mortgage Payment (P&I):-$0
– Operating Expenses (Tax, Ins, Maint, HOA):-$0
= Net Monthly Cash Flow:$0
Understanding the Results
The output of this calculator helps you evaluate the deal based on three critical real estate metrics:
Monthly Cash Flow: This is the profit you take home each month after paying the mortgage and all operating expenses. A positive cash flow ensures the property pays for itself.
Cash on Cash Return (CoC): This measures the return on the actual cash you invested (down payment + closing costs). It is calculated as (Annual Cash Flow / Total Cash Invested) × 100. Many investors target a CoC of 8-12% or higher.
Cap Rate (Capitalization Rate): This metric helps you compare the profitability of properties regardless of how they are financed. It is calculated as (Net Operating Income / Purchase Price) × 100.
Frequently Asked Questions
What is a "good" cash flow per door?
While this varies by market, many investors follow the "$100/door rule," meaning a single-family rental should generate at least $100 in pure profit per month after all expenses and reserves. In high-cost-of-living areas, investors might accept lower cash flow in exchange for higher appreciation potential.
Why should I include vacancy and maintenance?
New investors often make the mistake of calculating cash flow based solely on rent minus mortgage. However, roofs leak, tenants move out, and taxes rise. Allocating a percentage (typically 5-10%) for vacancy and maintenance ensures you have reserves when these inevitable costs arise.
How does the loan term affect cash flow?
A 30-year loan typically offers lower monthly payments compared to a 15-year loan, resulting in higher monthly cash flow. However, a 15-year loan builds equity faster and saves significantly on total interest paid. This calculator assumes a standard amortization schedule.
function calculateRental() {
// 1. Get Input Values
var price = parseFloat(document.getElementById('purchasePrice').value);
var downPercent = parseFloat(document.getElementById('downPayment').value);
var interestRate = parseFloat(document.getElementById('interestRate').value);
var years = parseFloat(document.getElementById('loanTerm').value);
var rent = parseFloat(document.getElementById('rentalIncome').value);
var vacancyPercent = parseFloat(document.getElementById('vacancyRate').value);
var annualTax = parseFloat(document.getElementById('propertyTax').value);
var annualInsurance = parseFloat(document.getElementById('insurance').value);
var maintPercent = parseFloat(document.getElementById('maintenance').value);
var hoa = parseFloat(document.getElementById('otherExpenses').value);
// Validation
if (isNaN(price) || isNaN(downPercent) || isNaN(interestRate) || isNaN(rent)) {
alert("Please enter valid numbers in all fields.");
return;
}
// 2. Perform Calculations
// Loan Calculations
var downPaymentAmount = price * (downPercent / 100);
var loanAmount = price – downPaymentAmount;
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = years * 12;
// Mortgage P&I Formula
var monthlyMortgage = 0;
if (interestRate === 0) {
monthlyMortgage = loanAmount / numberOfPayments;
} else {
monthlyMortgage = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
}
// Operating Expenses
var monthlyVacancyCost = rent * (vacancyPercent / 100);
var monthlyMaintenanceCost = rent * (maintPercent / 100);
var monthlyTax = annualTax / 12;
var monthlyInsurance = annualInsurance / 12;
var totalOperatingExpenses = monthlyVacancyCost + monthlyMaintenanceCost + monthlyTax + monthlyInsurance + hoa;
// Net Operating Income (NOI) = Revenue – Operating Expenses (Excluding Mortgage)
var effectiveGrossIncome = rent – monthlyVacancyCost;
var monthlyNOI = effectiveGrossIncome – (monthlyMaintenanceCost + monthlyTax + monthlyInsurance + hoa);
var annualNOI = monthlyNOI * 12;
// Cash Flow
var totalMonthlyExpenses = monthlyMortgage + totalOperatingExpenses;
var monthlyCashFlow = rent – totalMonthlyExpenses;
var annualCashFlow = monthlyCashFlow * 12;
// ROI Metrics
// Cash Invested (Down Payment + Closing Costs). For simplicity, we assume 2% closing costs roughly, or just use Down Payment if specific field not requested.
// Let's stick strictly to Down Payment to keep math traceable for user unless we added a closing cost field.
var totalCashInvested = downPaymentAmount;
var cashOnCash = 0;
if (totalCashInvested > 0) {
cashOnCash = (annualCashFlow / totalCashInvested) * 100;
}
var capRate = 0;
if (price > 0) {
capRate = (annualNOI / price) * 100;
}
// 3. Update DOM
// Formatting function
function formatMoney(num) {
return "$" + num.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
}
document.getElementById('resCashFlow').innerHTML = formatMoney(monthlyCashFlow);
document.getElementById('resCashFlow').className = monthlyCashFlow >= 0 ? "value positive" : "value negative";
document.getElementById('resCoc').innerHTML = cashOnCash.toFixed(2) + "%";
document.getElementById('resCoc').className = cashOnCash >= 0 ? "value positive" : "value negative";
document.getElementById('resCap').innerHTML = capRate.toFixed(2) + "%";
// Breakdown
document.getElementById('outGrossRent').innerHTML = formatMoney(rent);
document.getElementById('outVacancy').innerHTML = "-" + formatMoney(monthlyVacancyCost);
document.getElementById('outEffective').innerHTML = formatMoney(effectiveGrossIncome);
document.getElementById('outMortgage').innerHTML = "-" + formatMoney(monthlyMortgage);
// Combine Op Expenses for display
var displayOpExpenses = monthlyMaintenanceCost + monthlyTax + monthlyInsurance + hoa;
document.getElementById('outExpenses').innerHTML = "-" + formatMoney(displayOpExpenses);
document.getElementById('outNet').innerHTML = formatMoney(monthlyCashFlow);
document.getElementById('outNet').style.color = monthlyCashFlow >= 0 ? "#28a745" : "#dc3545";
// Show Results
document.getElementById('results').style.display = "block";
// Scroll to results
document.getElementById('results').scrollIntoView({behavior: "smooth"});
}