Choosing between leasing and buying a vehicle is one of the most significant financial decisions for most households. While both get you behind the wheel of a new car, the financial mechanics, ownership rights, and long-term costs differ drastically.
How the Math Works
Financing (Buying): When you buy a car, you are paying for the entire value of the vehicle plus interest. Your monthly payment is determined by the loan amount (Price minus Down Payment), the interest rate, and the loan term. Once the loan is paid off, you own the asset outright, which carries "equity" value.
Leasing: A lease is essentially a long-term rental. You are only paying for the depreciation that occurs during the period you drive the car, plus a finance charge (known as the Money Factor). This usually results in lower monthly payments, but you must return the car or pay the residual value at the end of the term.
Key Factors to Consider
Mileage: Leases come with strict mileage limits (typically 10,000 to 15,000 miles per year). If you drive long distances, buying is almost always better.
Customization: If you enjoy modifying your vehicle, leasing is not for you, as the car must be returned in original condition.
Equity: When you buy, your payments build equity. When you lease, you are paying for the "use" of the car, and you walk away with no asset at the end.
Maintenance: Leased vehicles are usually under the manufacturer's warranty for the entire term, reducing unexpected repair costs.
Example Comparison
Imagine a $35,000 SUV with a $5,000 down payment.
Scenario A (Buy): 60-month loan at 5.5% interest. Your monthly payment would be roughly $573. After 5 years, you own a car potentially worth $15,000.
Scenario B (Lease): 36-month lease with a $21,000 residual value. Your monthly payment might be closer to $420. After 3 years, you return the car and need a new down payment for your next vehicle.
function calculateLeaseVsBuy() {
// Inputs
var price = parseFloat(document.getElementById('vehiclePrice').value);
var down = parseFloat(document.getElementById('downPayment').value);
var taxRate = parseFloat(document.getElementById('salesTax').value) / 100;
var termMonths = parseFloat(document.getElementById('loanTerm').value);
var apr = parseFloat(document.getElementById('interestRate').value) / 100;
var residual = parseFloat(document.getElementById('residualValue').value);
// Error checking
if (isNaN(price) || isNaN(down) || isNaN(termMonths) || price 0) {
buyMonthly = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, termMonths)) / (Math.pow(1 + monthlyRate, termMonths) – 1);
} else {
buyMonthly = loanAmount / termMonths;
}
var buyTotalCost = (buyMonthly * termMonths) + down;
// — LEASE CALCULATION —
// Money Factor (Estimate if APR provided)
var moneyFactor = apr / 24;
var netCapCost = price – down;
var monthlyDepreciation = (netCapCost – residual) / termMonths;
var monthlyFinanceCharge = (netCapCost + residual) * moneyFactor;
var leaseMonthlyBase = monthlyDepreciation + monthlyFinanceCharge;
var leaseMonthly = leaseMonthlyBase * (1 + taxRate);
var leaseTotalCost = (leaseMonthly * termMonths) + down;
// Display Results
document.getElementById('buyMonthly').innerHTML = "$" + buyMonthly.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('buyTotal').innerHTML = "$" + buyTotalCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('leaseMonthly').innerHTML = "$" + leaseMonthly.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('leaseTotal').innerHTML = "$" + leaseTotalCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
// Summary Logic
var diff = buyMonthly – leaseMonthly;
var summaryBox = document.getElementById('analysisSummary');
if (diff > 0) {
summaryBox.innerHTML = "Leasing saves you $" + diff.toFixed(2) + " per month compared to buying, but remember: you won't own the car at the end of the term.";
} else {
summaryBox.innerHTML = "In this scenario, financing is actually comparable or cheaper per month due to the high residual value or low interest rates.";
}
document.getElementById('calcResults').style.display = 'block';
}