Please enter valid numeric values for Vehicle Price, Interest Rate, and Loan Term.
Estimated Monthly Payment
$0.00
Total Loan Amount
$0.00
Total Interest Paid
$0.00
Total Cost of Car
$0.00
Understanding Your Auto Loan Calculation
Purchasing a vehicle is one of the most significant financial decisions many people make, second only to buying a home. Our Auto Loan Calculator helps you navigate the complexities of financing a car by providing a clear breakdown of your potential monthly payments and total interest costs.
How This Calculator Works
To get the most accurate estimate, it is essential to understand the variables that impact your auto loan:
Vehicle Price: The sticker price or negotiated price of the car you intend to buy.
Down Payment: Cash paid upfront. A larger down payment reduces the principal loan amount and, consequently, the interest paid over time.
Trade-In Value: The amount the dealership offers for your current vehicle, which acts as credit toward the new purchase.
Sales Tax: Often overlooked, state and local sales taxes are added to the vehicle price before the loan is calculated.
Interest Rate (APR): The annual percentage rate charged by the lender. This is influenced by your credit score and current market rates.
Loan Term: The duration of the loan in months. Common terms are 36, 48, 60, 72, or even 84 months.
The Impact of Loan Terms on Monthly Payments
Many buyers are tempted to choose a longer loan term (e.g., 72 or 84 months) to lower their monthly payment. While this makes the monthly budget more manageable, it significantly increases the Total Interest Paid over the life of the loan. Conversely, a shorter term increases your monthly obligation but saves you money in the long run.
Tips for Getting the Best Auto Loan Rate
Check Your Credit Score: Before visiting a dealership, know your credit standing. Higher scores generally qualify for lower APRs.
Shop Around: Don't just accept the dealer's financing. Check rates with local banks and credit unions first to have a baseline for negotiation.
Put More Down: Aim for a down payment of at least 20% to avoid being "upside-down" on your loan (owing more than the car is worth) as soon as you drive off the lot.
Calculating Sales Tax and Fees
This calculator adds the sales tax to the vehicle price minus the trade-in value (in most states, trade-ins reduce the taxable amount). Be aware that additional dealership fees (like documentation fees) are not included here and should be factored into your final budget.
function calculateAutoLoan() {
// 1. Get references to input elements
var priceInput = document.getElementById("vehiclePrice");
var downPaymentInput = document.getElementById("downPayment");
var tradeInInput = document.getElementById("tradeInValue");
var taxInput = document.getElementById("salesTax");
var rateInput = document.getElementById("interestRate");
var termInput = document.getElementById("loanTerm");
// 2. Get values and parse to floats
var price = parseFloat(priceInput.value);
var down = parseFloat(downPaymentInput.value) || 0;
var trade = parseFloat(tradeInInput.value) || 0;
var taxRate = parseFloat(taxInput.value) || 0;
var interestRate = parseFloat(rateInput.value);
var months = parseFloat(termInput.value);
// 3. Validation
var errorDiv = document.getElementById("errorDisplay");
if (isNaN(price) || isNaN(interestRate) || isNaN(months) || price <= 0 || months <= 0) {
errorDiv.style.display = "block";
document.getElementById("resultsSection").style.display = "none";
return;
} else {
errorDiv.style.display = "none";
}
// 4. Specific Calculation Logic for Auto Loans
// Calculate Taxable Amount: (Price – TradeIn) is standard in many states, though some tax full price.
// We will assume Trade-In reduces taxable amount for this specific calculation logic.
var taxableAmount = Math.max(0, price – trade);
var taxAmount = taxableAmount * (taxRate / 100);
// Total Price including Tax
var totalPrice = price + taxAmount;
// Net Loan Amount = Total Price – Down Payment – Trade In
var loanAmount = totalPrice – down – trade;
// Handle case where down payment + trade in covers the cost
if (loanAmount <= 0) {
document.getElementById("monthlyPaymentResult").innerHTML = "$0.00";
document.getElementById("loanAmountResult").innerHTML = "$0.00";
document.getElementById("totalInterestResult").innerHTML = "$0.00";
document.getElementById("totalCostResult").innerHTML = "$" + totalPrice.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("resultsSection").style.display = "block";
return;
}
// Monthly Interest Rate
var monthlyRate = (interestRate / 100) / 12;
// Amortization Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPayment = 0;
if (monthlyRate === 0) {
monthlyPayment = loanAmount / months;
} else {
monthlyPayment = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, months)) / (Math.pow(1 + monthlyRate, months) – 1);
}
// Total Cost Calculation
var totalPayment = monthlyPayment * months;
var totalInterest = totalPayment – loanAmount;
var totalCostOfCar = totalPrice + totalInterest;
// 5. Output Results
document.getElementById("monthlyPaymentResult").innerHTML = "$" + monthlyPayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("loanAmountResult").innerHTML = "$" + loanAmount.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("totalInterestResult").innerHTML = "$" + totalInterest.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("totalCostResult").innerHTML = "$" + totalCostOfCar.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
// Show result section
document.getElementById("resultsSection").style.display = "block";
}