Mortgage Payment Calculator
body {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: #333;
margin: 0;
padding: 20px;
background-color: #f9f9f9;
}
.calculator-wrapper {
max-width: 800px;
margin: 0 auto;
background: #fff;
border-radius: 8px;
box-shadow: 0 4px 15px rgba(0,0,0,0.1);
overflow: hidden;
}
.calc-header {
background-color: #2c3e50;
color: #fff;
padding: 20px;
text-align: center;
}
.calc-header h2 {
margin: 0;
font-size: 24px;
}
.calc-body {
padding: 30px;
display: flex;
flex-wrap: wrap;
gap: 30px;
}
.input-section {
flex: 1;
min-width: 300px;
}
.result-section {
flex: 1;
min-width: 300px;
background-color: #f0f4f8;
padding: 20px;
border-radius: 6px;
display: flex;
flex-direction: column;
justify-content: center;
}
.form-group {
margin-bottom: 20px;
}
.form-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #555;
}
.input-wrapper {
position: relative;
}
.input-wrapper input {
width: 100%;
padding: 12px;
padding-left: 12px;
border: 1px solid #ddd;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.currency-symbol {
position: absolute;
left: 10px;
top: 50%;
transform: translateY(-50%);
color: #777;
}
.percent-symbol {
position: absolute;
right: 10px;
top: 50%;
transform: translateY(-50%);
color: #777;
}
.input-with-icon {
padding-left: 25px !important;
}
button.calc-btn {
width: 100%;
padding: 15px;
background-color: #27ae60;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background-color 0.2s;
}
button.calc-btn:hover {
background-color: #219150;
}
.result-card {
text-align: center;
margin-bottom: 20px;
padding-bottom: 20px;
border-bottom: 1px solid #ddd;
}
.result-card:last-child {
border-bottom: none;
margin-bottom: 0;
padding-bottom: 0;
}
.result-label {
font-size: 14px;
color: #777;
text-transform: uppercase;
letter-spacing: 1px;
margin-bottom: 5px;
}
.result-value {
font-size: 32px;
font-weight: 800;
color: #2c3e50;
}
.result-value.secondary {
font-size: 24px;
color: #555;
}
.content-article {
max-width: 800px;
margin: 40px auto;
background: #fff;
padding: 30px;
border-radius: 8px;
box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}
.content-article h2 {
color: #2c3e50;
border-bottom: 2px solid #eee;
padding-bottom: 10px;
margin-top: 0;
}
.content-article h3 {
color: #34495e;
margin-top: 25px;
}
.content-article p {
margin-bottom: 15px;
color: #444;
}
.content-article ul {
margin-bottom: 15px;
padding-left: 20px;
}
.content-article li {
margin-bottom: 8px;
}
@media (max-width: 600px) {
.calc-body {
flex-direction: column;
}
.result-section {
order: -1;
}
}
Monthly Payment
$1,769.83
Total Interest Paid
$357,138.60
Total Cost of Loan
$637,138.60
Understanding Your Mortgage Calculation
Buying a home is one of the most significant financial decisions you will make in your lifetime. Understanding how your mortgage payments are calculated is crucial for budgeting and long-term financial planning. This Mortgage Payment Calculator helps you estimate your monthly financial obligation based on key factors like home price, down payment, interest rate, and loan term.
How the Mortgage Formula Works
The standard formula used to calculate a fixed-rate mortgage monthly payment is:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
- M = Total monthly payment
- P = Principal loan amount (Home Price minus Down Payment)
- i = Monthly interest rate (Annual Interest Rate divided by 12)
- n = Total number of payments (Loan Term in years multiplied by 12)
Key Factors Affecting Your Mortgage
Several variables influence the final amount you pay each month:
- Home Price & Down Payment: The difference between these two figures determines your principal loan amount. A larger down payment reduces the principal, thereby lowering your monthly payments and the total interest paid over the life of the loan.
- Interest Rate: Even a fraction of a percentage point can significantly impact your monthly payment and total loan cost. Rates fluctuate based on economic conditions and your credit score.
- Loan Term: A standard 30-year term offers lower monthly payments but results in higher total interest costs compared to a 15-year term, which has higher monthly payments but saves money in the long run.
Why Use a Mortgage Calculator?
Using a calculator allows you to test different scenarios. You can see how increasing your down payment affects your monthly budget or how a different interest rate changes the total cost of the home. It empowers you to shop for homes within a realistic price range and negotiate loan terms with confidence.
function calculateMortgage() {
// 1. Get Input Values
var homePriceInput = document.getElementById('homePrice');
var downPaymentInput = document.getElementById('downPayment');
var loanTermInput = document.getElementById('loanTerm');
var interestRateInput = document.getElementById('interestRate');
var homePrice = parseFloat(homePriceInput.value);
var downPayment = parseFloat(downPaymentInput.value);
var loanTermYears = parseFloat(loanTermInput.value);
var annualRate = parseFloat(interestRateInput.value);
// 2. Validate Inputs
if (isNaN(homePrice) || homePrice < 0) {
alert("Please enter a valid Home Price.");
return;
}
if (isNaN(downPayment) || downPayment < 0) {
alert("Please enter a valid Down Payment.");
return;
}
if (isNaN(loanTermYears) || loanTermYears <= 0) {
alert("Please enter a valid Loan Term in years.");
return;
}
if (isNaN(annualRate) || annualRate = home price
if (principal <= 0) {
document.getElementById('monthlyPaymentResult').innerHTML = "$0.00";
document.getElementById('totalInterestResult').innerHTML = "$0.00";
document.getElementById('totalPaymentResult').innerHTML = "$" + downPayment.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('payoffDateResult').innerHTML = "N/A";
return;
}
var monthlyRate = (annualRate / 100) / 12;
var numberOfPayments = loanTermYears * 12;
var monthlyPayment = 0;
// Handle zero interest rate edge case
if (annualRate === 0) {
monthlyPayment = principal / numberOfPayments;
} else {
// Standard Amortization Formula: M = P[r(1+r)^n]/[(1+r)^n-1]
var x = Math.pow(1 + monthlyRate, numberOfPayments);
monthlyPayment = (principal * x * monthlyRate) / (x – 1);
}
var totalPayment = monthlyPayment * numberOfPayments;
var totalInterest = totalPayment – principal;
// Calculate Payoff Date
var today = new Date();
var payoffDate = new Date(today.setMonth(today.getMonth() + numberOfPayments));
var monthNames = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"];
var payoffString = monthNames[payoffDate.getMonth()] + " " + payoffDate.getFullYear();
// 4. Update UI with Results
// Using toLocaleString for currency formatting
document.getElementById('monthlyPaymentResult').innerHTML = "$" + monthlyPayment.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('totalInterestResult').innerHTML = "$" + totalInterest.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('totalPaymentResult').innerHTML = "$" + totalPayment.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('payoffDateResult').innerHTML = payoffString;
}
// Initialize calculation on load to show example state
window.onload = function() {
calculateMortgage();
};