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Rental Property Cash Flow Calculator

Purchase & Financing

Income & Expenses

Investment Analysis Results

Monthly Mortgage (P&I):
Total Monthly Expenses:
Monthly Net Cash Flow:
Annual Cash Flow:
Cap Rate:
Cash on Cash Return:

How to Calculate Rental Property Cash Flow

Analyzing a real estate investment requires more than just looking at the monthly rent. Professional investors use specific metrics to determine if a property is a "deal" or a "dud." This calculator helps you break down the four pillars of rental property returns: Income, Expenses, Debt Service, and Cash Flow.

The Cash Flow Formula

The basic math for rental cash flow is:

Net Cash Flow = Gross Rental Income - (Mortgage + Taxes + Insurance + Maintenance + Vacancy + Management)

Key Metrics Explained

  • Cap Rate (Capitalization Rate): This measures the property's natural rate of return without considering financing. It is calculated by dividing the Net Operating Income (NOI) by the purchase price.
  • Cash on Cash (CoC) Return: This is the "yield" on the actual money you out-of-pocket. If you put $60,000 down and make $6,000 in annual cash flow, your CoC is 10%.
  • Maintenance & CapEx: Many beginners forget these. You should set aside 5-15% of rent for repairs (maintenance) and big-ticket items like roofs or water heaters (Capital Expenditures).

Example Scenario

Imagine you buy a house for $300,000 with 20% down ($60,000). Your monthly rent is $2,500. After paying the mortgage ($1,517), taxes ($300), insurance ($100), and setting aside 10% for maintenance ($250), your monthly cash flow is approximately $333. This represents a 6.6% Cash on Cash return.

function calculateRentalCashFlow() { // Inputs var purchasePrice = parseFloat(document.getElementById('purchasePrice').value) || 0; var downPaymentPct = parseFloat(document.getElementById('downPaymentPct').value) || 0; var interestRate = parseFloat(document.getElementById('interestRate').value) || 0; var loanTerm = parseFloat(document.getElementById('loanTerm').value) || 0; var monthlyRent = parseFloat(document.getElementById('monthlyRent').value) || 0; var annualTaxes = parseFloat(document.getElementById('annualTaxes').value) || 0; var annualInsurance = parseFloat(document.getElementById('annualInsurance').value) || 0; var maintenancePct = parseFloat(document.getElementById('maintenancePct').value) || 0; // Logic var downPaymentAmount = purchasePrice * (downPaymentPct / 100); var loanAmount = purchasePrice – downPaymentAmount; // Monthly Mortgage Calculation (P&I) var monthlyInterest = (interestRate / 100) / 12; var numberOfPayments = loanTerm * 12; var monthlyMortgage = 0; if (interestRate > 0) { monthlyMortgage = loanAmount * (monthlyInterest * Math.pow(1 + monthlyInterest, numberOfPayments)) / (Math.pow(1 + monthlyInterest, numberOfPayments) – 1); } else { monthlyMortgage = loanAmount / numberOfPayments; } // Operating Expenses var monthlyTaxes = annualTaxes / 12; var monthlyInsurance = annualInsurance / 12; var monthlyMaintenance = monthlyRent * (maintenancePct / 100); var totalMonthlyExpenses = monthlyMortgage + monthlyTaxes + monthlyInsurance + monthlyMaintenance; var netMonthlyCashFlow = monthlyRent – totalMonthlyExpenses; var netAnnualCashFlow = netMonthlyCashFlow * 12; // ROI Metrics var annualNOI = (monthlyRent – monthlyTaxes – monthlyInsurance – monthlyMaintenance) * 12; var capRate = (annualNOI / purchasePrice) * 100; var cashOnCash = (netAnnualCashFlow / downPaymentAmount) * 100; // Display Results document.getElementById('resultsArea').style.display = 'block'; document.getElementById('resMortgage').innerText = '$' + monthlyMortgage.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('resTotalExp').innerText = '$' + totalMonthlyExpenses.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('resCashFlow').innerText = '$' + netMonthlyCashFlow.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('resAnnualCashFlow').innerText = '$' + netAnnualCashFlow.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('resCapRate').innerText = capRate.toFixed(2) + '%'; document.getElementById('resCoC').innerText = cashOnCash.toFixed(2) + '%'; // Smooth scroll to results document.getElementById('resultsArea').scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }

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