#mortgage-amortization-calculator-wrapper {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
max-width: 800px;
margin: 0 auto;
color: #333;
line-height: 1.6;
}
.mac-calculator-card {
background: #f9f9f9;
border: 1px solid #e0e0e0;
border-radius: 8px;
padding: 25px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.mac-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
@media (max-width: 600px) {
.mac-grid { grid-template-columns: 1fr; }
}
.mac-input-group {
margin-bottom: 15px;
}
.mac-input-group label {
display: block;
margin-bottom: 5px;
font-weight: 600;
font-size: 14px;
}
.mac-input-group input {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.mac-btn {
background-color: #2c3e50;
color: white;
border: none;
padding: 12px 20px;
font-size: 16px;
border-radius: 4px;
cursor: pointer;
width: 100%;
font-weight: bold;
transition: background 0.3s;
margin-top: 10px;
}
.mac-btn:hover {
background-color: #34495e;
}
.mac-results {
margin-top: 25px;
padding-top: 20px;
border-top: 2px solid #eee;
display: none;
}
.mac-highlight-box {
background: #fff;
padding: 15px;
border-left: 5px solid #27ae60;
margin-bottom: 20px;
box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}
.mac-result-row {
display: flex;
justify-content: space-between;
margin-bottom: 10px;
font-size: 15px;
}
.mac-result-val {
font-weight: 700;
color: #2c3e50;
}
.mac-large-val {
font-size: 24px;
color: #27ae60;
}
.mac-table-container {
margin-top: 20px;
overflow-x: auto;
max-height: 400px;
overflow-y: auto;
border: 1px solid #ddd;
}
.mac-schedule-table {
width: 100%;
border-collapse: collapse;
font-size: 13px;
}
.mac-schedule-table th, .mac-schedule-table td {
padding: 8px 12px;
text-align: right;
border-bottom: 1px solid #ddd;
}
.mac-schedule-table th {
background-color: #2c3e50;
color: white;
position: sticky;
top: 0;
text-align: center;
}
.mac-schedule-table tr:nth-child(even) {
background-color: #f2f2f2;
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.mac-article h2 {
color: #2c3e50;
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padding-bottom: 10px;
margin-top: 30px;
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.mac-article h3 {
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margin-top: 25px;
}
.mac-article p {
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.mac-article ul {
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padding-left: 20px;
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.mac-article li {
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function calculateMortgageAmortization() {
// 1. Get Input Values
var loanAmount = parseFloat(document.getElementById('mac_loan_amount').value);
var interestRate = parseFloat(document.getElementById('mac_interest_rate').value);
var loanTermYears = parseFloat(document.getElementById('mac_loan_term').value);
var startYear = parseInt(document.getElementById('mac_start_year').value);
// 2. Input Validation
if (isNaN(loanAmount) || loanAmount <= 0) {
alert("Please enter a valid Loan Amount.");
return;
}
if (isNaN(interestRate) || interestRate < 0) {
alert("Please enter a valid Interest Rate.");
return;
}
if (isNaN(loanTermYears) || loanTermYears <= 0) {
alert("Please enter a valid Loan Term.");
return;
}
// 3. Calculation Variables
var monthlyRate = interestRate / 100 / 12;
var totalPayments = loanTermYears * 12;
// 4. Monthly Payment Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var x = Math.pow(1 + monthlyRate, totalPayments);
var monthlyPayment = 0;
if (interestRate === 0) {
monthlyPayment = loanAmount / totalPayments;
} else {
monthlyPayment = (loanAmount * x * monthlyRate) / (x – 1);
}
// 5. Generate Amortization Schedule
var balance = loanAmount;
var totalInterest = 0;
var scheduleHTML = "";
var currentYear = startYear;
var yearInterest = 0;
var yearPrincipal = 0;
for (var i = 1; i <= totalPayments; i++) {
var interestPayment = balance * monthlyRate;
var principalPayment = monthlyPayment – interestPayment;
// Handle last payment rounding differences
if (balance < principalPayment) {
principalPayment = balance;
// Adjust monthly payment for the very last month just for calculation accuracy in totals
}
balance -= principalPayment;
totalInterest += interestPayment;
yearInterest += interestPayment;
yearPrincipal += principalPayment;
// End of year or end of loan aggregation for the table
if (i % 12 === 0 || balance <= 0.01) {
scheduleHTML += "";
scheduleHTML += "" + currentYear + " ";
scheduleHTML += "$" + yearInterest.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,') + " ";
scheduleHTML += "$" + yearPrincipal.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,') + " ";
scheduleHTML += "$" + (balance > 0 ? balance : 0).toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,') + " ";
scheduleHTML += " ";
currentYear++;
yearInterest = 0;
yearPrincipal = 0;
}
if (balance <= 0) break;
}
var totalCost = loanAmount + totalInterest;
var payoffYear = startYear + Math.ceil(totalPayments / 12) – 1;
// Get month name for payoff date (approximate based on term)
var payoffDateString = "End of " + payoffYear;
// 6. Display Results
document.getElementById('mac_monthly_payment').innerText = "$" + monthlyPayment.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
document.getElementById('mac_total_principal').innerText = "$" + loanAmount.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
document.getElementById('mac_total_interest').innerText = "$" + totalInterest.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
document.getElementById('mac_total_cost').innerText = "$" + totalCost.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
document.getElementById('mac_payoff_date').innerText = payoffDateString;
document.getElementById('mac_schedule_body').innerHTML = scheduleHTML;
document.getElementById('mac_results_area').style.display = 'block';
}
Mortgage Amortization Calculator
Estimated Monthly Payment:
$0.00
Total Principal:
$0.00
Total Interest Paid:
$0.00
Total Cost of Loan:
$0.00
Payoff Date:
–
Amortization Schedule (Yearly Summary)
| Year | Interest Paid | Principal Paid | Ending Balance |
|---|
Understanding Your Mortgage Amortization
A mortgage amortization calculator is an essential tool for any homebuyer or homeowner looking to understand the true cost of their home loan over time. Unlike a simple loan estimate, an amortization schedule breaks down every payment you make for the life of the loan, showing exactly how much goes toward the bank's profit (interest) versus paying down your debt (principal).
What is Amortization?
Amortization refers to the process of spreading out a loan into a series of fixed payments over time. While your total monthly payment remains constant for fixed-rate mortgages, the composition of that payment changes drastically over the years.
- Early Years: The majority of your payment goes toward interest. This is front-loaded, meaning you build equity slowly at the beginning.
- Later Years: As the loan balance decreases, less interest accrues, and more of your payment is applied to the principal balance.
How to Use This Calculator
To get the most accurate results from this specific mortgage calculator, input the following details:
- Loan Amount: The initial amount borrowed from the lender (Home Price minus Down Payment).
- Interest Rate: The annual percentage rate (APR) provided by your lender. Even a small difference here can impact the total interest by tens of thousands of dollars.
- Loan Term: The duration of the loan, typically 15 or 30 years. Shorter terms have higher monthly payments but significantly lower total interest costs.
Strategies to Save on Interest
Using the amortization schedule above, you can see the impact of time on your finances. Here are proven strategies to reduce the total cost of your mortgage:
- Make Bi-Weekly Payments: Instead of paying monthly, pay half your mortgage payment every two weeks. This results in one extra full payment per year, shortening a 30-year loan by roughly 4-5 years.
- Refinance to a Shorter Term: If rates drop or your income increases, refinancing from a 30-year to a 15-year loan accelerates equity building.
- Principal-Only Payments: Any extra money added to your check should be designated as "principal only." This directly reduces the balance on which future interest is calculated.
Why the Amortization Schedule Matters
Many homeowners are shocked to see that on a 30-year loan, the total interest paid often equals or exceeds the original loan amount. For example, on a $300,000 loan at 7% interest, you might pay over $400,000 in interest alone. Visualizing this data helps you make informed decisions about refinancing, prepayment, and home affordability.