Purchasing a vehicle is a significant financial decision, and understanding your monthly auto loan payment is crucial for effective budgeting. This calculator helps you estimate your monthly payment for an auto loan with Navy Federal Credit Union, based on the loan amount, interest rate, and loan term.
How the Calculator Works
The calculator uses a standard formula for calculating monthly loan payments (M):
$M = P \frac{r(1+r)^n}{(1+r)^n – 1}$
Where:
M = Your total monthly loan payment
P = The principal loan amount (the total amount you borrow)
r = Your monthly interest rate (annual rate divided by 12)
n = The total number of payments over the loan's lifetime (loan term in years multiplied by 12)
For example, if you borrow $30,000 at an annual interest rate of 6.5% for 5 years:
P = $30,000
Annual rate = 6.5% = 0.065
Monthly rate (r) = 0.065 / 12 = 0.00541667
Loan term = 5 years
Total number of payments (n) = 5 * 12 = 60
Plugging these values into the formula provides an estimated monthly payment. Our calculator automates this process for you, also showing the total interest paid and the total amount repaid over the life of the loan.
Why Use This Calculator?
Budgeting: Determine affordability before you shop for a car.
Comparison: Compare different loan scenarios (e.g., a shorter term with higher payment vs. a longer term with lower payment but more interest).
Negotiation: Understand how interest rates and loan terms affect your overall cost.
Navy Federal Specifics: While this calculator uses the standard formula, Navy Federal may have specific loan products or promotional rates. Always confirm final figures with Navy Federal Credit Union.
This tool provides an estimate. Factors like down payments, taxes, fees, and specific Navy Federal loan programs can influence your actual monthly payment. We recommend using this as a planning tool and consulting directly with Navy Federal Credit Union for official loan terms and pre-approval.
function updateRateFromSlider(value) {
var rate = parseFloat(value) / 10;
document.getElementById("interestRate").value = rate.toFixed(1);
// Recalculate immediately if values are already entered
if (document.getElementById("loanAmount").value && document.getElementById("loanTerm").value) {
calculatePayment();
}
}
function updateSliderFromRate() {
var rate = parseFloat(document.getElementById("interestRate").value);
document.getElementById("interestRateSlider").value = rate * 10;
}
function calculatePayment() {
var loanAmount = parseFloat(document.getElementById("loanAmount").value);
var annualInterestRate = parseFloat(document.getElementById("interestRate").value);
var loanTermYears = parseInt(document.getElementById("loanTerm").value);
var resultDiv = document.getElementById("result");
var monthlyPaymentDisplay = document.getElementById("monthlyPayment");
var totalInterestDisplay = document.getElementById("totalInterest");
var totalRepaidDisplay = document.getElementById("totalRepaid");
// Clear previous results and show loading/calculation message
monthlyPaymentDisplay.textContent = "Calculating…";
totalInterestDisplay.textContent = "";
totalRepaidDisplay.textContent = "";
// Input validation
if (isNaN(loanAmount) || loanAmount <= 0) {
monthlyPaymentDisplay.textContent = "Please enter a valid loan amount.";
return;
}
if (isNaN(annualInterestRate) || annualInterestRate < 0) {
monthlyPaymentDisplay.textContent = "Please enter a valid annual interest rate.";
return;
}
if (isNaN(loanTermYears) || loanTermYears 0) {
monthlyPayment = loanAmount * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
} else {
// Handle 0% interest rate case
monthlyPayment = loanAmount / numberOfPayments;
}
var totalRepaid = monthlyPayment * numberOfPayments;
var totalInterest = totalRepaid – loanAmount;
// Format currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
});
monthlyPaymentDisplay.textContent = formatter.format(monthlyPayment);
totalInterestDisplay.textContent = "Total Interest Paid: " + formatter.format(totalInterest);
totalRepaidDisplay.textContent = "Total Amount Repaid: " + formatter.format(totalRepaid);
// Ensure slider is updated if rate is changed manually
updateSliderFromRate();
}
// Initial calculation on load if default values exist
document.addEventListener('DOMContentLoaded', function() {
calculatePayment();
});