Please enter valid positive numbers for Price and Interest Rate.
Monthly Payment:$0.00
Total Loan Amount:$0.00
Total Interest Paid:$0.00
Total Cost (Price + Tax + Interest):$0.00
*Estimates include sales tax on the full vehicle price.
function calculateAutoLoan() {
// 1. Get input values
var price = parseFloat(document.getElementById("vehiclePrice").value);
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 interestRate = parseFloat(document.getElementById("interestRate").value);
var termMonths = parseInt(document.getElementById("loanTerm").value);
var errorDiv = document.getElementById("errorMsg");
var resultsDiv = document.getElementById("resultsArea");
// 2. Validation
if (isNaN(price) || price <= 0 || isNaN(interestRate) || interestRate < 0) {
errorDiv.style.display = "block";
resultsDiv.style.display = "none";
return;
}
errorDiv.style.display = "none";
// 3. Calculation Logic
// Calculate Tax (Simplification: Tax on full price)
var taxAmount = price * (taxRate / 100);
// Calculate Loan Principal
// Principal = Price + Tax – Down Payment – Trade In
var principal = price + taxAmount – down – trade;
if (principal <= 0) {
// No loan needed
resultsDiv.style.display = "block";
document.getElementById("displayMonthlyPayment").innerText = "$0.00";
document.getElementById("displayLoanAmount").innerText = "$0.00";
document.getElementById("displayTotalInterest").innerText = "$0.00";
document.getElementById("displayTotalCost").innerText = "$" + (price + taxAmount).toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
return;
}
var monthlyPayment = 0;
var totalInterest = 0;
if (interestRate === 0) {
monthlyPayment = principal / termMonths;
totalInterest = 0;
} else {
var monthlyRate = (interestRate / 100) / 12;
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var x = Math.pow(1 + monthlyRate, termMonths);
monthlyPayment = (principal * x * monthlyRate) / (x – 1);
totalInterest = (monthlyPayment * termMonths) – principal;
}
var totalCost = price + taxAmount + totalInterest;
// 4. Update UI
resultsDiv.style.display = "block";
document.getElementById("displayMonthlyPayment").innerText = "$" + monthlyPayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("displayLoanAmount").innerText = "$" + principal.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("displayTotalInterest").innerText = "$" + totalInterest.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("displayTotalCost").innerText = "$" + totalCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
}
Understanding Your Auto Loan Options
Buying a car is one of the most significant purchases most people make, second only to buying a home. Navigating the world of auto financing can be complex, but using our Auto Loan Calculator can help you estimate your monthly payments and understand the total cost of your vehicle over time. Whether you are looking at a brand-new sedan, a used SUV, or a truck, knowing the numbers before you walk into the dealership gives you leverage.
How This Calculator Works
This tool takes several key factors into account to provide an accurate estimate of your financial obligation. Here is a breakdown of the inputs:
Vehicle Price: The negotiated price of the car before taxes and fees.
Down Payment: Cash you pay upfront. A higher down payment reduces the loan principal and monthly costs.
Trade-In Value: The amount the dealer offers for your old vehicle, which acts like a down payment.
Sales Tax: The percentage charged by your state or local government. This calculator adds tax to the total price.
Interest Rate (APR): The annual percentage rate charged by the lender. Your credit score significantly impacts this number.
Loan Term: The duration of the loan. Common terms differ from 36 to 72 months.
The Impact of Loan Terms on Your Budget
One of the most important decisions you will make is choosing the loan term. While a longer term (like 72 or 84 months) lowers your monthly payment, it often drastically increases the Total Interest Paid. Conversely, a shorter term (36 or 48 months) increases your monthly obligation but saves you money in the long run.
For example, financing $25,000 at 5% interest:
48 Months: Higher monthly payment, but less interest paid overall.
72 Months: Lower monthly payment, but you pay interest for two extra years.
Tips for Getting the Best Auto Loan Rate
Before applying for a car loan, check your credit score. Lenders reserve their best "advertised" rates for borrowers with excellent credit (typically 720+). If your score is lower, you may face higher APRs. Consider getting pre-approved by a bank or credit union before visiting the dealership. This "blank check" approach often secures a better rate than dealer financing and prevents the dealer from marking up the interest rate.
What About Additional Fees?
Remember that the "Out the Door" price of a car includes more than just the sticker price and tax. You should also budget for:
Documentation Fees: Charged by the dealer for processing paperwork.
Registration and Title Fees: Paid to the state DMV.
Insurance: Lenders require full coverage insurance on financed vehicles.
Use the "Total Cost" field in our calculator to ensure the vehicle fits within your overall financial plan, not just your monthly budget.