Buying a new or used car is a significant financial commitment. This calculator helps you understand exactly how much you will pay each month and over the life of the loan based on the vehicle price, your down payment, trade-in value, and financing terms.
Understanding the Key Factors
Vehicle Price: The negotiated purchase price of the car before taxes and fees.
Trade-In Value: The amount the dealership offers for your current vehicle, which reduces the taxable amount in many states.
APR (Interest Rate): The annual percentage rate charged by the lender. A lower credit score typically results in a higher APR.
Loan Term: How long you have to repay the loan. Longer terms (e.g., 72 or 84 months) lower your monthly payment but significantly increase the total interest paid.
Strategies to Lower Your Monthly Payment
If the calculated monthly payment is higher than your budget allows, consider these strategies:
Increase your down payment: Paying more upfront reduces the principal loan amount.
Improve your credit score: Better credit qualifies you for lower interest rates.
Choose a less expensive vehicle: Sticking to a budget prevents becoming "upside-down" on your loan.
Shorten the term: While this increases the monthly payment, it saves thousands in interest in the long run.
Note: This calculator provides estimates for educational purposes. Actual loan terms may vary based on lender fees, title costs, and registration fees.
function calculateAutoLoan() {
// Get input values
var price = parseFloat(document.getElementById('vehiclePrice').value) || 0;
var down = parseFloat(document.getElementById('downPayment').value) || 0;
var trade = parseFloat(document.getElementById('tradeInValue').value) || 0;
var taxRate = parseFloat(document.getElementById('salesTax').value) || 0;
var apr = parseFloat(document.getElementById('interestRate').value) || 0;
var term = parseInt(document.getElementById('loanTerm').value) || 60;
// Validation
if (price <= 0) {
alert("Please enter a valid vehicle price.");
return;
}
// Logic
// In most states, sales tax is applied to the price minus the trade-in value
var taxableAmount = price – trade;
if (taxableAmount < 0) taxableAmount = 0;
var taxAmount = taxableAmount * (taxRate / 100);
var totalPriceWithTax = price + taxAmount;
// Loan Amount = Total Price + Tax – Trade In – Down Payment
var loanAmount = totalPriceWithTax – trade – down;
if (loanAmount <= 0) {
document.getElementById('resultContainer').style.display = 'block';
document.getElementById('displayMonthly').innerHTML = "$0.00";
document.getElementById('displayLoanAmount').innerHTML = "$0.00";
document.getElementById('displayTotalInterest').innerHTML = "$0.00";
document.getElementById('displayTotalCost').innerHTML = "$" + (down + trade).toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
return;
}
var monthlyInterestRate = (apr / 100) / 12;
var monthlyPayment = 0;
var totalInterest = 0;
var totalCost = 0;
if (monthlyInterestRate === 0) {
// Simple division if 0% interest
monthlyPayment = loanAmount / term;
totalInterest = 0;
} else {
// Amortization formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var mathPower = Math.pow(1 + monthlyInterestRate, term);
monthlyPayment = loanAmount * ((monthlyInterestRate * mathPower) / (mathPower – 1));
totalInterest = (monthlyPayment * term) – loanAmount;
}
totalCost = price + taxAmount + totalInterest;
// Display Results
document.getElementById('resultContainer').style.display = 'block';
document.getElementById('displayMonthly').innerHTML = "$" + monthlyPayment.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('displayLoanAmount').innerHTML = "$" + loanAmount.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('displayTotalInterest').innerHTML = "$" + totalInterest.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('displayTotalCost').innerHTML = "$" + totalCost.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
}