Online Loan Amortization Calculator
Understanding Loan Amortization
A loan amortization schedule is a table detailing each periodic payment on an amortizing loan (like a mortgage, car loan, or personal loan) over time. Each payment is broken down into two components: interest and principal. Initially, a larger portion of your payment goes towards interest, and a smaller portion goes towards reducing the principal balance. As time progresses, this ratio shifts, with more of each payment applied to the principal and less to interest. This gradual reduction of the loan balance is the essence of amortization.
How the Calculator Works:
This calculator helps you understand the repayment structure of your loan. It takes three key inputs:
- Loan Amount: The total sum of money borrowed.
- Annual Interest Rate: The yearly cost of borrowing, expressed as a percentage.
- Loan Term (Years): The total duration over which the loan will be repaid.
Using these inputs, the calculator determines your fixed monthly payment and then generates an amortization schedule. This schedule shows you:
- The breakdown of each monthly payment into interest and principal.
- The remaining loan balance after each payment.
- The total interest paid and total principal paid over the life of the loan.
By understanding your amortization schedule, you can better manage your finances, track your progress in paying down debt, and potentially explore options for making extra payments to save on interest.
Key Terms Explained:
- Principal: The original amount of money borrowed.
- Interest: The cost of borrowing money, usually expressed as a percentage of the principal.
- Amortization Period: The length of time over which a loan is repaid.
- Monthly Payment: The fixed amount paid each month towards the loan, covering both principal and interest.
- Remaining Balance: The amount of the loan that still needs to be repaid after a certain number of payments.
function calculateAmortization() {
var loanAmount = parseFloat(document.getElementById("loanAmount").value);
var annualInterestRate = parseFloat(document.getElementById("annualInterestRate").value);
var loanTermYears = parseFloat(document.getElementById("loanTermYears").value);
var resultDiv = document.getElementById("amortizationResult");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(loanAmount) || isNaN(annualInterestRate) || isNaN(loanTermYears) || loanAmount <= 0 || annualInterestRate < 0 || loanTermYears <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
var monthlyInterestRate = annualInterestRate / 100 / 12;
var numberOfPayments = loanTermYears * 12;
// Calculate monthly payment using the standard loan payment formula
var monthlyPayment = loanAmount * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
if (isNaN(monthlyPayment) || !isFinite(monthlyPayment)) {
resultDiv.innerHTML = "Could not calculate monthly payment. Please check your inputs.";
return;
}
var tableHTML = "
Amortization Schedule
";
tableHTML += "
Monthly Payment: $" + monthlyPayment.toFixed(2) + "";
tableHTML += "
| Payment # | Date | Interest Paid | Principal Paid | Remaining Balance |
|---|
";
var remainingBalance = loanAmount;
var totalInterestPaid = 0;
var totalPrincipalPaid = 0;
var currentDate = new Date();
for (var i = 1; i <= numberOfPayments; i++) {
var interestForThisMonth = remainingBalance * monthlyInterestRate;
var principalForThisMonth = monthlyPayment – interestForThisMonth;
// Adjust the last payment to ensure the balance is exactly zero
if (i === numberOfPayments) {
principalForThisMonth = remainingBalance;
monthlyPayment = interestForThisMonth + principalForThisMonth; // Adjust final payment if needed
totalInterestPaid += interestForThisMonth;
totalPrincipalPaid += principalForThisMonth;
remainingBalance = 0;
} else {
totalInterestPaid += interestForThisMonth;
totalPrincipalPaid += principalForThisMonth;
remainingBalance -= principalForThisMonth;
}
// Ensure remaining balance doesn't go negative due to rounding
if (remainingBalance < 0.01) {
remainingBalance = 0;
}
// Add month to date for display
currentDate.setMonth(currentDate.getMonth() + 1);
var monthYear = currentDate.toLocaleString('default', { month: 'short', year: 'numeric' });
tableHTML += "";
tableHTML += "| " + i + " | ";
tableHTML += "" + monthYear + " | ";
tableHTML += "$" + interestForThisMonth.toFixed(2) + " | ";
tableHTML += "$" + principalForThisMonth.toFixed(2) + " | ";
tableHTML += "$" + remainingBalance.toFixed(2) + " | ";
tableHTML += "
";
}
tableHTML += "
";
tableHTML += "
Total Interest Paid: $" + totalInterestPaid.toFixed(2) + "";
tableHTML += "
Total Principal Paid: $" + totalPrincipalPaid.toFixed(2) + "";
resultDiv.innerHTML = tableHTML;
}
.calculator-container {
font-family: sans-serif;
max-width: 800px;
margin: 20px auto;
padding: 20px;
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