.calculator-container-wrapper {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 0 auto;
color: #333;
line-height: 1.6;
}
.calc-box {
background: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 30px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.calc-title {
text-align: center;
margin-bottom: 25px;
color: #2c3e50;
font-size: 24px;
font-weight: 700;
}
.calc-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
.calc-group {
margin-bottom: 15px;
}
.calc-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
font-size: 14px;
color: #495057;
}
.calc-group input, .calc-group select {
width: 100%;
padding: 12px;
border: 1px solid #ced4da;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
transition: border-color 0.2s;
}
.calc-group input:focus {
border-color: #007bff;
outline: none;
}
.calc-btn-row {
grid-column: 1 / -1;
text-align: center;
margin-top: 10px;
}
.calc-btn {
background-color: #007bff;
color: white;
border: none;
padding: 14px 30px;
font-size: 16px;
font-weight: 600;
border-radius: 4px;
cursor: pointer;
transition: background-color 0.2s;
}
.calc-btn:hover {
background-color: #0056b3;
}
.result-box {
grid-column: 1 / -1;
background: #fff;
border: 1px solid #dee2e6;
border-radius: 6px;
padding: 20px;
margin-top: 20px;
display: none;
}
.result-row {
display: flex;
justify-content: space-between;
padding: 10px 0;
border-bottom: 1px solid #eee;
}
.result-row:last-child {
border-bottom: none;
}
.result-label {
color: #6c757d;
}
.result-value {
font-weight: 700;
color: #2c3e50;
font-size: 18px;
}
.result-highlight {
font-size: 28px;
color: #28a745;
}
.error-msg {
color: #dc3545;
text-align: center;
display: none;
margin-top: 10px;
grid-column: 1 / -1;
}
.article-content {
margin-top: 50px;
padding-top: 20px;
border-top: 2px solid #eee;
}
.article-content h2 {
font-size: 26px;
color: #2c3e50;
margin-bottom: 20px;
}
.article-content h3 {
font-size: 20px;
color: #34495e;
margin-top: 25px;
margin-bottom: 15px;
}
.article-content p {
margin-bottom: 15px;
font-size: 16px;
}
.article-content ul {
margin-bottom: 20px;
padding-left: 20px;
}
.article-content li {
margin-bottom: 10px;
}
@media (max-width: 600px) {
.calc-grid {
grid-template-columns: 1fr;
}
}
function calculateAutoLoan() {
var vehiclePrice = document.getElementById("vehiclePrice").value;
var salesTaxRate = document.getElementById("salesTax").value;
var downPayment = document.getElementById("downPayment").value;
var tradeIn = document.getElementById("tradeIn").value;
var interestRate = document.getElementById("interestRate").value;
var loanTerm = document.getElementById("loanTerm").value;
var errorMsg = document.getElementById("errorMsg");
var resultBox = document.getElementById("resultBox");
// Clean inputs
var priceVal = parseFloat(vehiclePrice) || 0;
var taxRateVal = parseFloat(salesTaxRate) || 0;
var downVal = parseFloat(downPayment) || 0;
var tradeVal = parseFloat(tradeIn) || 0;
var interestVal = parseFloat(interestRate);
var termVal = parseFloat(loanTerm);
// Validation
if (priceVal <= 0 || isNaN(interestVal) || isNaN(termVal)) {
errorMsg.style.display = "block";
errorMsg.innerText = "Please enter a valid Vehicle Price, Interest Rate, and Loan Term.";
resultBox.style.display = "none";
return;
}
errorMsg.style.display = "none";
// Calculation Logic
// 1. Calculate Tax (Assuming tax is applied to price minus trade-in, common in many states, otherwise tax on full price)
// We will use conservative method: Tax on Full Price for this generic calculator
var taxAmount = priceVal * (taxRateVal / 100);
// 2. Calculate Principal Needed
var principal = priceVal + taxAmount – downVal – tradeVal;
if (principal <= 0) {
errorMsg.style.display = "block";
errorMsg.innerText = "Down payment and trade-in value exceed the car price. No loan needed!";
resultBox.style.display = "none";
return;
}
// 3. Calculate Monthly Payment
var monthlyRate = (interestVal / 100) / 12;
var monthlyPayment = 0;
if (interestVal === 0) {
monthlyPayment = principal / termVal;
} else {
var x = Math.pow(1 + monthlyRate, termVal);
monthlyPayment = (principal * x * monthlyRate) / (x – 1);
}
// 4. Calculate Totals
var totalPaid = monthlyPayment * termVal;
var totalInterest = totalPaid – principal;
var totalCostOfCar = priceVal + taxAmount + totalInterest;
// Display Results
document.getElementById("monthlyPaymentResult").innerText = formatCurrency(monthlyPayment);
document.getElementById("totalLoanAmount").innerText = formatCurrency(principal);
document.getElementById("totalTax").innerText = formatCurrency(taxAmount);
document.getElementById("totalInterest").innerText = formatCurrency(totalInterest);
document.getElementById("totalCost").innerText = formatCurrency(totalCostOfCar);
resultBox.style.display = "block";
}
function formatCurrency(num) {
return "$" + num.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}
Understanding Your Auto Loan
Purchasing a vehicle is one of the most significant financial decisions many people make, second only to buying a home. Using this Auto Loan Calculator allows you to estimate your monthly payments accurately before heading to the dealership. By inputting your potential car price, down payment, and expected interest rate, you can determine exactly how much car you can afford without breaking your monthly budget.
How the Car Loan Formula Works
Your monthly car payment is determined by three primary factors: the loan amount (principal), the annual percentage rate (APR), and the loan term (length of the loan). This calculator uses the standard amortization formula:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
- M = Total monthly payment
- P = Principal loan amount (Vehicle Price + Tax – Down Payment – Trade-in)
- i = Monthly interest rate (APR divided by 12)
- n = Number of months required to repay the loan
The Impact of Down Payments and Trade-Ins
Increasing your down payment or trading in an older vehicle significantly reduces your Loan-to-Value (LTV) ratio. A lower LTV means you are borrowing less money relative to the car's worth. This has two major benefits: it lowers your monthly payment and often qualifies you for a better interest rate from lenders because the loan is considered less risky.
Choosing the Right Loan Term
While a 72 or 84-month loan may look attractive because it offers a lower monthly payment, it is important to consider the total cost of interest. As shown in the "Total Interest Paid" result above, extending your loan term increases the total amount you pay for the vehicle over time. A 60-month term is often considered the "sweet spot" between affordability and minimizing interest costs.
Don't Forget Sales Tax
Many buyers forget to factor in state sales tax, which can add thousands of dollars to the final "out-the-door" price. This calculator includes a field for sales tax to ensure your loan estimate is realistic. Remember that in many states, you only pay sales tax on the difference between the new car price and your trade-in value, potentially saving you money.