Mortgage Amortization Schedule Calculator
body {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
line-height: 1.6;
color: #333;
background-color: #f8f9fa;
margin: 0;
padding: 20px;
}
.loan-calc-container {
max-width: 900px;
margin: 30px auto;
background-color: #ffffff;
padding: 30px;
border-radius: 8px;
box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
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h1, h2 {
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margin-bottom: 20px;
}
.input-group {
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button:hover {
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#scheduleResult {
margin-top: 30px;
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border-radius: 4px;
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#scheduleResult h3 {
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.amortization-table {
width: 100%;
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margin-top: 20px;
font-size: 0.9rem;
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.amortization-table th, .amortization-table td {
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Mortgage Amortization Schedule Calculator
Understanding Your Mortgage Amortization Schedule
A mortgage amortization schedule is a table that breaks down your monthly mortgage payment into principal and interest components over the life of your loan. It shows how much of each payment goes towards paying down the loan balance and how much is applied to interest. Understanding this schedule is crucial for any homeowner as it provides clarity on your debt repayment journey and the total cost of borrowing.
The Math Behind Amortization
The core of amortization calculation involves determining the fixed monthly payment and then dissecting each payment. Here's a breakdown:
1. Calculating the Monthly Payment (M)
The standard formula for calculating the monthly mortgage payment uses the following variables:
- P: The principal loan amount (the total amount borrowed).
- r: The monthly interest rate, calculated by dividing the annual interest rate by 12 (e.g., 4.5% annual rate becomes 0.045 / 12 = 0.00375 monthly).
- n: The total number of payments, calculated by multiplying the loan term in years by 12 (e.g., a 30-year loan has 30 * 12 = 360 payments).
The formula for the monthly payment (M) is:
M = P [ r(1 + r)^n ] / [ (1 + r)^n – 1]
2. Amortization Schedule Breakdown
For each payment period (usually monthly), the schedule details:
- Beginning Balance: The outstanding loan balance at the start of the payment period.
- Monthly Payment: The fixed amount paid each month (calculated above).
- Interest Paid: The portion of the monthly payment that covers interest for that period. This is calculated as: Beginning Balance * Monthly Interest Rate (r).
- Principal Paid: The portion of the monthly payment that reduces the loan balance. This is calculated as: Monthly Payment – Interest Paid.
- Ending Balance: The loan balance remaining after the payment is applied. This is calculated as: Beginning Balance – Principal Paid.
This process repeats for every payment until the ending balance reaches zero.
Why Use an Amortization Schedule Calculator?
- Financial Planning: Predict your total interest paid over the loan's life and the principal reduction over time.
- Early Payoff Strategy: See how extra payments affect the principal balance and how much interest you can save.
- Loan Comparison: Compare different loan offers (varying rates or terms) to understand the long-term financial impact.
- Budgeting: Accurately forecast your housing expenses for years to come.
- Tax Deductions: Mortgage interest is often tax-deductible. The schedule helps track this amount.
Our calculator provides a clear, month-by-month view of your mortgage repayment, empowering you with the knowledge to make informed financial decisions.
function calculateAmortization() {
var loanAmount = parseFloat(document.getElementById("loanAmount").value);
var annualInterestRate = parseFloat(document.getElementById("annualInterestRate").value);
var loanTermYears = parseInt(document.getElementById("loanTermYears").value);
var resultDiv = document.getElementById("scheduleResult");
resultDiv.innerHTML = "; // Clear previous results
var errorMessageDiv = document.createElement('div');
errorMessageDiv.className = 'error-message';
if (isNaN(loanAmount) || loanAmount <= 0) {
errorMessageDiv.textContent = "Please enter a valid positive Loan Amount.";
resultDiv.appendChild(errorMessageDiv);
return;
}
if (isNaN(annualInterestRate) || annualInterestRate < 0) {
errorMessageDiv.textContent = "Please enter a valid non-negative Annual Interest Rate.";
resultDiv.appendChild(errorMessageDiv);
return;
}
if (isNaN(loanTermYears) || loanTermYears 0) {
monthlyPayment = loanAmount * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
} else {
monthlyPayment = loanAmount / numberOfPayments; // Handle 0% interest case
}
var totalInterestPaid = 0;
var beginningBalance = loanAmount;
var amortizationData = [];
for (var i = 0; i < numberOfPayments; i++) {
var interestPayment = beginningBalance * monthlyInterestRate;
var principalPayment = monthlyPayment – interestPayment;
// Adjust last payment to ensure balance is exactly zero
if (i === numberOfPayments – 1) {
principalPayment = beginningBalance; // Pay off remaining balance
interestPayment = monthlyPayment – principalPayment; // Recalculate interest for last payment
if (interestPayment < 0) interestPayment = 0; // Ensure no negative interest if balance was tiny
}
var endingBalance = beginningBalance – principalPayment;
// Handle potential floating point inaccuracies for the last payment
if (endingBalance < 0.01 && i === numberOfPayments – 1) {
endingBalance = 0;
}
amortizationData.push({
paymentNumber: i + 1,
beginningBalance: beginningBalance,
monthlyPayment: monthlyPayment,
interestPayment: interestPayment,
principalPayment: principalPayment,
endingBalance: endingBalance
});
totalInterestPaid += interestPayment;
beginningBalance = endingBalance;
}
// Display Results
var html = '
Amortization Schedule Summary
';
html += '
';
html += 'Total Loan Amount: $' + loanAmount.toFixed(2) + ";
html += 'Monthly Payment: $' + monthlyPayment.toFixed(2) + ";
html += 'Total Interest Paid: $' + totalInterestPaid.toFixed(2) + ";
html += 'Total Cost of Loan: $' + (loanAmount + totalInterestPaid).toFixed(2);
html += '
';
html += '
';
html += '| Month | Beginning Balance | Payment | Interest | Principal | Ending Balance |
|---|
';
html += '';
// Limit the number of rows displayed for very long terms, e.g., first 10 and last 5
var maxRowsToShow = 10;
var rowsToDisplay = [];
if (amortizationData.length <= maxRowsToShow * 2) {
rowsToDisplay = amortizationData;
} else {
for (var i = 0; i < maxRowsToShow; i++) {
rowsToDisplay.push(amortizationData[i]);
}
rowsToDisplay.push({ paymentNumber: '…', beginningBalance: '', monthlyPayment: '', interestPayment: '', principalPayment: '', endingBalance: '' }); // Separator
for (var i = amortizationData.length – 5; i < amortizationData.length; i++) {
rowsToDisplay.push(amortizationData[i]);
}
}
for (var i = 0; i < rowsToDisplay.length; i++) {
var row = rowsToDisplay[i];
if (row.paymentNumber === '…') {
html += '| … |
';
} else {
html += '';
html += '| ' + row.paymentNumber + ' | ';
html += '$' + row.beginningBalance.toFixed(2) + ' | ';
html += '$' + row.monthlyPayment.toFixed(2) + ' | ';
html += '$' + row.interestPayment.toFixed(2) + ' | ';
html += '$' + row.principalPayment.toFixed(2) + ' | ';
html += '$' + row.endingBalance.toFixed(2) + ' | ';
html += '
';
}
}
html += '
';
resultDiv.innerHTML = html;
}