function calculateLease() {
var msrp = parseFloat(document.getElementById('msrp').value);
var resPct = parseFloat(document.getElementById('residualPercent').value);
var down = parseFloat(document.getElementById('downPayment').value) || 0;
var trade = parseFloat(document.getElementById('tradeIn').value) || 0;
var mf = parseFloat(document.getElementById('moneyFactor').value);
var term = parseInt(document.getElementById('leaseTerm').value);
var taxRate = parseFloat(document.getElementById('salesTax').value);
if (isNaN(msrp) || isNaN(resPct) || isNaN(mf) || isNaN(term) || term <= 0) {
alert("Please enter valid numbers for all fields.");
return;
}
// 1. Calculate Gross Cap Cost
var netCapCost = msrp – down – trade;
// 2. Calculate Residual Value
var residualValue = msrp * (resPct / 100);
// 3. Monthly Depreciation
var depreciationFee = (netCapCost – residualValue) / term;
if (depreciationFee < 0) depreciationFee = 0;
// 4. Monthly Finance Fee (Rent Charge)
var financeFee = (netCapCost + residualValue) * mf;
// 5. Pre-tax Subtotal
var subtotal = depreciationFee + financeFee;
// 6. Total with Tax
var monthlyTax = subtotal * (taxRate / 100);
var totalMonthly = subtotal + monthlyTax;
// 7. Total Lease Cost (Payments + Down)
var totalLeaseCost = (totalMonthly * term) + down + trade;
// Update UI
document.getElementById('monthly-payment').innerText = '$' + totalMonthly.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-depreciation').innerText = '$' + depreciationFee.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-finance').innerText = '$' + financeFee.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-tax').innerText = '$' + monthlyTax.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-total-cost').innerText = '$' + totalLeaseCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('result-area').style.display = 'block';
}
Understanding Your Car Lease Calculation
Leasing a vehicle is often more complex than a standard car loan. Instead of paying for the entire value of the car, you are essentially paying for the depreciation of the vehicle over a set period, plus interest and taxes.
Key Lease Components Explained
MSRP: The Manufacturer's Suggested Retail Price. This is the starting point for negotiations.
Residual Value: This is the estimated value of the car at the end of the lease. A higher residual value means a lower monthly payment because the car "holds" more of its value.
Money Factor: This represents the interest rate. To convert the Money Factor to a standard APR, multiply it by 2400 (e.g., 0.0015 * 2400 = 3.6% APR).
Net Capitalized Cost: The MSRP minus any down payment, trade-in value, or dealer discounts. This is the actual amount being financed.
Calculation Example
Imagine you lease a $40,000 SUV with a 60% residual value for 36 months:
Depreciation: The car is expected to be worth $24,000 (60% of $40k) in 3 years. You must pay the $16,000 difference ($444/month).
Rent Charge: Using a money factor of 0.00125, the finance fee is calculated by adding the net cost and residual value then multiplying by the factor.
Total: Your payment is the sum of depreciation, finance fees, and local sales tax.
Tips for a Better Lease Deal
To lower your monthly payment, focus on three things: negotiating a lower sale price (Cap Cost), finding vehicles with high residual values (usually luxury brands or popular Japanese imports), and ensuring you have a competitive Money Factor based on your credit score.