Advanced Mortgage Calculator with Amortization
/* Scoped styles for the calculator to avoid theme conflicts */
.mc-calculator-container {
max-width: 800px;
margin: 0 auto;
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
color: #333;
line-height: 1.6;
padding: 20px;
background: #fff;
border: 1px solid #e0e0e0;
border-radius: 8px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.mc-calculator-wrapper {
display: flex;
flex-wrap: wrap;
gap: 20px;
margin-bottom: 30px;
}
.mc-input-group {
flex: 1 1 300px;
display: flex;
flex-direction: column;
gap: 15px;
}
.mc-field {
display: flex;
flex-direction: column;
}
.mc-field label {
font-weight: 600;
font-size: 0.9rem;
margin-bottom: 5px;
color: #444;
}
.mc-field input, .mc-field select {
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 1rem;
}
.mc-field input:focus {
border-color: #0073aa;
outline: none;
box-shadow: 0 0 0 2px rgba(0,115,170,0.2);
}
.mc-btn {
background-color: #0073aa;
color: white;
border: none;
padding: 12px 20px;
font-size: 1rem;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background-color 0.3s;
width: 100%;
margin-top: 10px;
}
.mc-btn:hover {
background-color: #005177;
}
.mc-results {
flex: 1 1 300px;
background-color: #f9f9f9;
padding: 20px;
border-radius: 6px;
border: 1px solid #eee;
}
.mc-result-item {
margin-bottom: 15px;
border-bottom: 1px solid #ddd;
padding-bottom: 10px;
}
.mc-result-item:last-child {
border-bottom: none;
}
.mc-result-label {
font-size: 0.9rem;
color: #666;
}
.mc-result-value {
font-size: 1.5rem;
font-weight: 700;
color: #2c3e50;
}
.mc-result-value.small {
font-size: 1.2rem;
}
.mc-error {
color: #d32f2f;
font-size: 0.9rem;
margin-top: 10px;
display: none;
}
.mc-article-content {
margin-top: 40px;
border-top: 2px solid #eee;
padding-top: 20px;
}
.mc-article-content h2 {
font-size: 1.8rem;
color: #2c3e50;
margin-bottom: 15px;
}
.mc-article-content h3 {
font-size: 1.4rem;
color: #2c3e50;
margin-top: 25px;
margin-bottom: 10px;
}
.mc-article-content p {
margin-bottom: 15px;
}
.mc-article-content ul {
margin-bottom: 15px;
padding-left: 20px;
}
.mc-article-content li {
margin-bottom: 8px;
}
/* Amortization Table Styles */
.mc-table-container {
overflow-x: auto;
margin-top: 20px;
max-height: 400px;
overflow-y: auto;
border: 1px solid #ddd;
}
.mc-table {
width: 100%;
border-collapse: collapse;
font-size: 0.9rem;
}
.mc-table th, .mc-table td {
padding: 10px;
text-align: right;
border-bottom: 1px solid #eee;
}
.mc-table th {
background-color: #f1f1f1;
position: sticky;
top: 0;
font-weight: 600;
text-align: right;
}
.mc-table th:first-child, .mc-table td:first-child {
text-align: center;
}
@media (max-width: 600px) {
.mc-calculator-wrapper {
flex-direction: column;
}
.mc-results {
order: -1;
}
}
Repayment Summary
Monthly Principal & Interest
$1,769.82
Total Interest Paid
$357,133.48
Total Cost of Loan
$637,133.48
| Year |
Interest Paid |
Principal Paid |
Remaining Balance |
Understanding Your Mortgage Amortization
Purchasing a home is likely the largest financial commitment you will make in your lifetime. Understanding how your mortgage works, specifically how your payments are divided between principal and interest, is crucial for long-term financial planning. This Mortgage Calculator helps you estimate your monthly payments and visualize the impact of interest rates and extra payments over time.
How is Your Mortgage Payment Calculated?
A standard fixed-rate mortgage payment consists primarily of two parts: Principal and Interest. In the early years of a long-term loan (like a 30-year mortgage), the majority of your payment goes toward interest. As time passes and the principal balance decreases, a larger portion of your payment goes toward reducing the principal.
- Principal: The money you borrowed to buy the house.
- Interest: The cost of borrowing that money, paid to the lender.
The Impact of Extra Payments
Making extra payments toward your principal can significantly reduce the total interest you pay and shorten your loan term. Even a small additional amount, such as $50 or $100 per month, works directly against the principal balance. Because interest is calculated based on the remaining balance, lowering the principal faster means less interest accrues in subsequent months.
What is an Amortization Schedule?
An amortization schedule is a table detailing each periodic payment on an amortizing loan. It breaks down how much of every payment goes toward interest versus principal and shows the remaining balance after each payment. Our calculator below provides a simplified annual view of this schedule to help you track your equity growth.
Factors That Affect Your Monthly Payment
Several variables influence how much you pay each month:
- Loan Amount: Derived from the home price minus your down payment. Lower borrowing means lower payments.
- Interest Rate: Higher rates increase the cost of borrowing significantly. A 1% difference can cost tens of thousands of dollars over the life of the loan.
- Loan Term: Shorter terms (e.g., 15 years) have higher monthly payments but lower total interest costs compared to longer terms (e.g., 30 years).
function calculateMortgage() {
// 1. Get Input Values
var homePrice = parseFloat(document.getElementById('mcHomePrice').value);
var downPayment = parseFloat(document.getElementById('mcDownPayment').value);
var interestRate = parseFloat(document.getElementById('mcInterestRate').value);
var loanTermYears = parseInt(document.getElementById('mcLoanTerm').value);
var extraPayment = parseFloat(document.getElementById('mcExtraPayment').value);
// 2. Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTermYears)) {
document.getElementById('mcError').style.display = 'block';
return;
}
if (extraPayment = home price
if (principal 0.01 && actualMonths = (balance + interestPart)) {
principalPart = balance;
totalMonthlyPay = balance + interestPart;
balance = 0;
} else {
principalPart = totalMonthlyPay – interestPart;
balance -= principalPart;
}
totalInterest += interestPart;
yearInterest += interestPart;
yearPrincipal += principalPart;
actualMonths++;
// Add to table if it's December or the loan is paid off
var checkDate = new Date();
checkDate.setMonth(currentMonth + actualMonths);
if (checkDate.getMonth() === 0 || balance === 0) {
tableHTML += "
" +
"| " + displayYear + " | " +
"$" + yearInterest.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + " | " +
"$" + yearPrincipal.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + " | " +
"$" + Math.max(0, balance).toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + " | " +
"
";
displayYear++;
yearInterest = 0;
yearPrincipal = 0;
}
}
// 5. Calculate Payoff Date
var payoffDateObj = new Date();
payoffDateObj.setMonth(payoffDateObj.getMonth() + actualMonths);
var monthNames = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"];
var payoffString = monthNames[payoffDateObj.getMonth()] + " " + payoffDateObj.getFullYear();
// 6. Display Results
document.getElementById('mcMonthlyPayment').innerText = "$" + monthlyPayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('mcTotalInterest').innerText = "$" + totalInterest.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
var totalCost = principal + totalInterest;
document.getElementById('mcTotalCost').innerText = "$" + totalCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('mcPayoffDate').innerText = payoffString;
// Show Table
document.getElementById('mcTableBody').innerHTML = tableHTML;
document.getElementById('mcAmortizationSchedule').style.display = 'block';
}
// Initial Calculation on Load
window.onload = function() {
calculateMortgage();
};