Loan Amortization Schedule Calculator
This calculator helps you understand how your loan payments are structured over time, breaking down how much of each payment goes towards the principal and how much goes towards interest.
.calculator-container {
font-family: Arial, sans-serif;
max-width: 800px;
margin: 20px auto;
padding: 20px;
border: 1px solid #ccc;
border-radius: 8px;
box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}
.inputs {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
gap: 15px;
margin-bottom: 20px;
}
.input-group {
display: flex;
flex-direction: column;
}
label {
margin-bottom: 5px;
font-weight: bold;
}
input[type="number"] {
padding: 8px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 1rem;
}
button {
padding: 10px 15px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 1rem;
cursor: pointer;
transition: background-color 0.2s ease;
}
button:hover {
background-color: #0056b3;
}
#amortizationResult {
margin-top: 20px;
}
#resultTitle {
color: #333;
border-bottom: 1px solid #eee;
padding-bottom: 10px;
margin-bottom: 15px;
}
#scheduleTableContainer table {
width: 100%;
border-collapse: collapse;
margin-top: 15px;
font-size: 0.9rem;
}
#scheduleTableContainer th,
#scheduleTableContainer td {
border: 1px solid #ddd;
padding: 8px;
text-align: right;
}
#scheduleTableContainer th {
background-color: #f2f2f2;
font-weight: bold;
text-align: center;
}
#scheduleTableContainer tr:nth-child(even) {
background-color: #f9f9f9;
}
#summaryStats {
margin-top: 20px;
padding: 15px;
background-color: #eef;
border-left: 5px solid #007bff;
border-radius: 4px;
}
#summaryStats p {
margin: 5px 0;
font-size: 1.1rem;
}
function calculateAmortization() {
var loanAmount = parseFloat(document.getElementById("loanAmount").value);
var annualInterestRate = parseFloat(document.getElementById("annualInterestRate").value);
var loanTermYears = parseInt(document.getElementById("loanTermYears").value);
var resultTitle = document.getElementById("resultTitle");
var scheduleTableContainer = document.getElementById("scheduleTableContainer");
var summaryStats = document.getElementById("summaryStats");
// Clear previous results
resultTitle.innerHTML = "";
scheduleTableContainer.innerHTML = "";
summaryStats.innerHTML = "";
// Input validation
if (isNaN(loanAmount) || isNaN(annualInterestRate) || isNaN(loanTermYears) || loanAmount <= 0 || annualInterestRate < 0 || loanTermYears <= 0) {
resultTitle.innerHTML = "Please enter valid numbers for all fields.";
return;
}
var monthlyInterestRate = (annualInterestRate / 100) / 12;
var numberOfPayments = loanTermYears * 12;
// Calculate monthly payment using the loan payment formula
// M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
var monthlyPayment = loanAmount * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
// Handle cases where the rate is 0
if (monthlyInterestRate === 0) {
monthlyPayment = loanAmount / numberOfPayments;
}
var remainingBalance = loanAmount;
var totalInterestPaid = 0;
var totalPrincipalPaid = 0;
var tableHtml = "
| Month | Payment | Principal | Interest | Remaining Balance |
|---|
";
for (var month = 1; month remainingBalance) {
principalPayment = remainingBalance;
monthlyPayment = principalPayment + interestPayment; // Adjust monthly payment for the final payment
}
remainingBalance -= principalPayment;
totalInterestPaid += interestPayment;
totalPrincipalPaid += principalPayment;
// Handle potential floating point issues for the last payment
if (month === numberOfPayments) {
remainingBalance = 0;
principalPayment = loanAmount – totalPrincipalPaid + principalPayment; // Adjust final principal
monthlyPayment = principalPayment + interestPayment; // Adjust final total payment
}
tableHtml += "";
tableHtml += "| " + month + " | ";
tableHtml += "$" + monthlyPayment.toFixed(2) + " | ";
tableHtml += "$" + principalPayment.toFixed(2) + " | ";
tableHtml += "$" + interestPayment.toFixed(2) + " | ";
tableHtml += "$" + remainingBalance.toFixed(2) + " | ";
tableHtml += "
";
}
tableHtml += "
";
resultTitle.innerHTML = "Loan Amortization Schedule";
scheduleTableContainer.innerHTML = tableHtml;
var summaryHtml = "
Total Paid: $" + (loanAmount + totalInterestPaid).toFixed(2) + "";
summaryHtml += "
Total Principal Paid: $" + loanAmount.toFixed(2) + "";
summaryHtml += "
Total Interest Paid: $" + totalInterestPaid.toFixed(2) + "";
summaryStats.innerHTML = summaryHtml;
}
Understanding Loan Amortization
A loan amortization schedule is a table detailing each periodic payment on an amortizing loan (like a mortgage or car loan) over time. Each payment is broken down into two components: principal and interest. As payments are made, the balance of the loan decreases.
How it Works:
- Monthly Payment Calculation: The fixed monthly payment is calculated using a formula that considers the loan amount (principal), the annual interest rate, and the loan term (duration).
- Interest Portion: In the early stages of the loan, a larger portion of your monthly payment goes towards paying the interest that has accrued on the outstanding balance. The interest for a given month is calculated on the remaining principal balance.
- Principal Portion: The remainder of your monthly payment, after the interest portion is covered, goes towards reducing the principal balance of the loan.
- As Time Progresses: With each subsequent payment, the principal balance decreases. This means the amount of interest accrued each month also decreases. Consequently, a larger portion of your fixed monthly payment starts going towards the principal.
- Loan Payoff: By the end of the loan term, the entire principal balance will have been paid off, along with all the accrued interest.
Example:
Let's say you take out a loan for $200,000 with an annual interest rate of 5% over a 30-year term.
- The calculated monthly payment would be approximately $1,073.64.
- In the first month, a significant portion of this payment (around $833.33) would go towards interest, and the rest (around $240.31) would reduce the principal.
- As you progress through the loan, say to month 180 (halfway through), your monthly payment of $1,073.64 would be split differently. More of it would be going towards principal reduction and less towards interest, even though the total payment remains the same.
- By the final payment, the entire remaining balance (which would be very small by then) and the final interest accrued would be paid off, leaving you with a $0 balance.
Use the calculator above to generate your own amortization schedule and see how your specific loan will be paid off over time!