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function calculateRentalCashFlow() {
// 1. Get Inputs
var price = parseFloat(document.getElementById('purchasePrice').value);
var downPay = parseFloat(document.getElementById('downPayment').value);
var rate = parseFloat(document.getElementById('interestRate').value);
var years = parseFloat(document.getElementById('loanTerm').value);
var closing = parseFloat(document.getElementById('closingCosts').value) || 0;
var rent = parseFloat(document.getElementById('monthlyRent').value);
var taxYear = parseFloat(document.getElementById('annualTax').value) || 0;
var insYear = parseFloat(document.getElementById('annualInsurance').value) || 0;
var hoa = parseFloat(document.getElementById('hoaFee').value) || 0;
var maintPercent = parseFloat(document.getElementById('maintenance').value) || 0;
// Validation
if (isNaN(price) || isNaN(downPay) || isNaN(rate) || isNaN(years) || isNaN(rent)) {
document.getElementById('errorMsg').style.display = 'block';
document.getElementById('calcResults').style.display = 'none';
return;
}
document.getElementById('errorMsg').style.display = 'none';
// 2. Calculations
var loanAmount = price – downPay;
var monthlyRate = (rate / 100) / 12;
var numPayments = years * 12;
// Mortgage P&I
var monthlyMortgage = 0;
if (loanAmount > 0 && rate > 0) {
monthlyMortgage = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numPayments)) / (Math.pow(1 + monthlyRate, numPayments) – 1);
} else if (loanAmount > 0 && rate === 0) {
monthlyMortgage = loanAmount / numPayments;
}
var monthlyTax = taxYear / 12;
var monthlyIns = insYear / 12;
var monthlyMaint = rent * (maintPercent / 100);
var totalMonthlyOperatingExp = monthlyTax + monthlyIns + hoa + monthlyMaint;
var totalMonthlyExp = totalMonthlyOperatingExp + monthlyMortgage;
var noiMonthly = rent – totalMonthlyOperatingExp;
var cashFlowMonthly = rent – totalMonthlyExp;
var cashFlowAnnual = cashFlowMonthly * 12;
var totalCashInvested = downPay + closing;
// Cash on Cash Return = Annual Cash Flow / Total Cash Invested
var cocReturn = 0;
if (totalCashInvested > 0) {
cocReturn = (cashFlowAnnual / totalCashInvested) * 100;
}
// Cap Rate = (Annual NOI / Purchase Price)
var capRate = 0;
if (price > 0) {
capRate = ((noiMonthly * 12) / price) * 100;
}
// 3. Update DOM
function fmt(num) {
return "$" + num.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
}
document.getElementById('displayCashFlow').innerText = fmt(cashFlowMonthly);
document.getElementById('displayCashFlow').style.color = cashFlowMonthly >= 0 ? '#27ae60' : '#c0392b';
document.getElementById('displayCoC').innerText = cocReturn.toFixed(2) + "%";
document.getElementById('displayCoC').style.color = cocReturn >= 0 ? '#2980b9' : '#c0392b';
document.getElementById('displayCapRate').innerText = capRate.toFixed(2) + "%";
document.getElementById('resIncome').innerText = fmt(rent);
document.getElementById('resMortgage').innerText = fmt(monthlyMortgage);
document.getElementById('resTax').innerText = fmt(monthlyTax);
document.getElementById('resInsurance').innerText = fmt(monthlyIns);
document.getElementById('resHOA').innerText = fmt(hoa);
document.getElementById('resMaint').innerText = fmt(monthlyMaint);
document.getElementById('resTotalExp').innerText = fmt(totalMonthlyExp);
document.getElementById('resNOI').innerText = fmt(noiMonthly);
document.getElementById('calcResults').style.display = 'block';
}
Rental Property Cash Flow Calculator
Purchase & Financing
Income & Expenses
Please fill in all required fields with valid numbers.
$0.00
Monthly Cash Flow
0.00%
Cash on Cash Return
0.00%
Cap Rate
Monthly Rental Income:
$0.00
– Monthly Mortgage (P&I):
$0.00
– Property Tax (Monthly):
$0.00
– Insurance (Monthly):
$0.00
– HOA & Fees:
$0.00
– Maintenance/Vacancy Reserve:
$0.00
Total Monthly Expenses:
$0.00
Net Operating Income (NOI) / Mo:
$0.00
How to Analyze Rental Property Investments
Investing in real estate is one of the most reliable ways to build long-term wealth, but success hinges on the numbers. A beautiful property isn't necessarily a profitable investment. This Rental Property Cash Flow Calculator helps you evaluate the financial viability of a potential purchase by analyzing three critical metrics: Cash Flow, Cash on Cash Return, and Cap Rate.
Understanding Key Investment Metrics
1. Monthly Cash Flow
Cash flow is the net profit you pocket every month after all expenses are paid. It is calculated as:
Cash Flow = Gross Rent – (Mortgage + Taxes + Insurance + HOA + Reserves)
Positive cash flow ensures the property pays for itself and provides passive income. Negative cash flow means you are losing money every month to hold the asset.
2. Cash on Cash Return (CoC)
While cash flow tells you the dollar amount you make, the Cash on Cash Return tells you how hard your money is working. It compares your annual profit to the actual cash you invested (Down Payment + Closing Costs).
- Formula: (Annual Cash Flow / Total Cash Invested) x 100
- Example: If you invest $50,000 to buy a house and it generates $5,000 in profit per year, your CoC return is 10%. This allows you to compare real estate returns directly against stocks or bonds.
3. Capitalization Rate (Cap Rate)
The Cap Rate measures the natural rate of return of the property assuming you bought it in cash (no loan). It helps compare the profitability of similar properties regardless of financing.
Formula: (Net Operating Income / Purchase Price) x 100.
Common Expenses to Watch For
Many new investors fail because they underestimate expenses. When using the calculator, ensure you account for:
- Vacancy Rates: No property is occupied 100% of the time. Setting aside 5-10% of rent for vacancy is a prudent safety net.
- Maintenance & Repairs: Roofs leak and toilets break. Allocating 10-15% of monthly rent for future repairs ensures you aren't caught off guard by large capital expenditures (CapEx).
- Property Management: Even if you plan to manage it yourself, it is wise to calculate the numbers as if you were paying a manager (typically 8-10% of rent) to ensure the deal still works if you decide to outsource later.
How to Use This Calculator
- Enter Purchase Details: Input the asking price and your financing terms. A higher down payment reduces the mortgage payment, increasing cash flow but potentially lowering your Cash on Cash return.
- Estimate Income: Research local rental listings (comps) to find a realistic monthly rent.
- Add Expenses: Input taxes, insurance, and HOA fees accurately. Don't forget to adjust the maintenance reserve percentage based on the property's age and condition.
- Analyze: Look for a positive cash flow and a CoC return that meets your investment goals (investors often aim for 8-12% or higher).