Car Loan Amortization Calculator and Payment Schedule
Understanding your auto loan is crucial before signing the paperwork at the dealership. A car loan amortization calculator goes beyond a simple monthly payment estimate; it shows you exactly how your payments are applied over the life of the loan. Amortization is the process of paying off debt with regular payments over time. In the early stages of your car loan, a larger portion of your monthly payment goes towards interest, while a smaller portion goes towards reducing the principal balance. As the loan matures, this shifts, and more of your payment goes towards the principal.
This specific calculator helps visualize the true cost of financing a vehicle. Factors like a substantial down payment or high trade-in equity can significantly reduce your loan principal, thereby lowering the total interest paid. Conversely, stretching a loan term out to 72 or 84 months will lower your monthly payment but vastly increase the total interest cost over the life of the loan. Use this tool to experiment with different interest rates (APRs) and terms to find the financing structure that best fits your budget.
Auto Loan Calculator
Vehicle Price ($):
Down Payment ($):
Trade-in Value ($):
Annual Interest Rate (APR %):
Loan Term (Months):
36 Months (3 Years)
48 Months (4 Years)
60 Months (5 Years)
72 Months (6 Years)
84 Months (7 Years)
Calculate Payment & Schedule
Loan Summary
Estimated Monthly Payment:
$0.00
Loan Principal Amount:
$0.00
Total Interest Paid:
$0.00
Total Cost of Car (Principal + Interest):
$0.00
Annual Amortization Schedule
Year
Interest Paid
Principal Paid
Remaining Balance
function calculateCarAmortization() {
// 1. Get Inputs
var vPriceStr = document.getElementById('vehiclePrice').value;
var dPaymentStr = document.getElementById('downPayment').value;
var tValueStr = document.getElementById('tradeInValue').value;
var iRateStr = document.getElementById('interestRate').value;
var lTermStr = document.getElementById('loanTermMonths').value;
var resultDiv = document.getElementById('result');
var errorDiv = document.getElementById('error-message');
var scheduleBody = document.getElementById('scheduleBody');
// Clear previous results and errors
resultDiv.style.display = 'none';
errorDiv.style.display = 'none';
scheduleBody.innerHTML = ";
// 2. Validate and Parse Inputs
var vehiclePrice = parseFloat(vPriceStr) || 0;
var downPayment = parseFloat(dPaymentStr) || 0;
var tradeInValue = parseFloat(tValueStr) || 0;
var annualInterestRate = parseFloat(iRateStr);
var loanTermMonths = parseInt(lTermStr);
if (vehiclePrice <= 0) {
errorDiv.innerText = "Please enter a valid Vehicle Price.";
errorDiv.style.display = 'block';
return;
}
if (isNaN(annualInterestRate) || annualInterestRate < 0) {
errorDiv.innerText = "Please enter a valid Interest Rate.";
errorDiv.style.display = 'block';
return;
}
// 3. Core Calculations
var principalLoanAmount = vehiclePrice – downPayment – tradeInValue;
if (principalLoanAmount <= 0) {
errorDiv.innerText = "Down payment and trade-in value exceed the vehicle price. No loan needed.";
errorDiv.style.display = 'block';
return;
}
var monthlyInterestRate = (annualInterestRate / 100) / 12;
var monthlyPayment = 0;
// Handle 0% interest edge case
if (monthlyInterestRate === 0) {
monthlyPayment = principalLoanAmount / loanTermMonths;
} else {
// Standard Amortization Formula: A = P * (r(1+r)^n) / ((1+r)^n – 1)
var mathPower = Math.pow(1 + monthlyInterestRate, loanTermMonths);
monthlyPayment = principalLoanAmount * (monthlyInterestRate * mathPower) / (mathPower – 1);
}
var totalCostOfLoan = monthlyPayment * loanTermMonths;
var totalInterestPaid = totalCostOfLoan – principalLoanAmount;
// 4. Display Summary Results
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById('monthlyPaymentResult').innerText = formatter.format(monthlyPayment);
document.getElementById('principalResult').innerText = formatter.format(principalLoanAmount);
document.getElementById('totalInterestResult').innerText = formatter.format(totalInterestPaid);
document.getElementById('totalCostResult').innerText = formatter.format(totalCostOfLoan);
// 5. Generate Amortization Schedule (Annual Summary)
var remainingBalance = principalLoanAmount;
var yearlyInterest = 0;
var yearlyPrincipal = 0;
var currentYear = 1;
var scheduleHTML = "";
for (var i = 1; i <= loanTermMonths; i++) {
var interestForMonth = remainingBalance * monthlyInterestRate;
var principalForMonth = monthlyPayment – interestForMonth;
// Adjust last payment for rounding differences
if (i === loanTermMonths) {
principalForMonth = remainingBalance;
interestForMonth = monthlyPayment – principalForMonth;
if(interestForMonth < 0) interestForMonth = 0; // Safety check
}
remainingBalance -= principalForMonth;
yearlyInterest += interestForMonth;
yearlyPrincipal += principalForMonth;
// If it's the end of a year or the very last payment, output the row
if (i % 12 === 0 || i === loanTermMonths) {
scheduleHTML += '
';
scheduleHTML += 'Example Year ' + currentYear + ' ';
scheduleHTML += '' + formatter.format(yearlyInterest) + ' ';
scheduleHTML += '' + formatter.format(yearlyPrincipal) + ' ';
scheduleHTML += '' + formatter.format(Math.max(0, remainingBalance)) + ' '; // Ensure no negative balance display
scheduleHTML += ' ';
// Reset yearly counters and increment year
yearlyInterest = 0;
yearlyPrincipal = 0;
currentYear++;
}
}
scheduleBody.innerHTML = scheduleHTML;
resultDiv.style.display = 'block';
}