Planning to buy a home? Use our comprehensive Mortgage Payment Calculator to estimate your monthly payments, interest costs, and total loan balance. Understanding your potential mortgage payments is the first crucial step in the home buying journey.
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Estimated Monthly Payment
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Total Principal
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Total Interest
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Total Cost of Loan
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How Mortgages Work
A mortgage is a loan specifically used to purchase real estate. When you take out a mortgage, the lender pays the seller the full price of the home upfront (minus your down payment), and you agree to pay back the lender over a set period, typically 15 or 30 years, along with interest.
Pro Tip: A larger down payment reduces your Principal amount, which not only lowers your monthly payment but can also save you tens of thousands of dollars in interest over the life of the loan.
Key Factors Affecting Your Payment
Loan Principal: This is the amount of money you borrow. It equals the home price minus your down payment.
Interest Rate: This is the cost of borrowing money. Even a small difference in rates (e.g., 0.5%) can significantly impact your monthly payment and total interest paid.
Loan Term: The length of time you have to repay the loan. A 30-year term offers lower monthly payments but results in higher total interest costs compared to a 15-year term.
Understanding Amortization
Mortgage loans are typically amortized, meaning your monthly payment is divided between paying off the interest and paying down the principal balance. In the early years of your mortgage, the majority of your payment goes toward interest. As the loan matures, a larger portion of your payment goes toward reducing the principal.
Why Calculate Before You Buy?
Using a mortgage calculator is essential for financial planning. It helps you determine your budget by showing you exactly how much house you can afford based on your income and expenses. Remember to also account for property taxes, homeowners insurance, and potential HOA fees, which are often added to your monthly mortgage bill.
function calculateMortgage() {
// 1. Get Input Values
var homePrice = parseFloat(document.getElementById('mc-home-price').value);
var downPayment = parseFloat(document.getElementById('mc-down-payment').value);
var annualRate = parseFloat(document.getElementById('mc-interest-rate').value);
var loanTermYears = parseFloat(document.getElementById('mc-loan-term').value);
// 2. Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(annualRate) || isNaN(loanTermYears)) {
alert("Please fill in all fields with valid numbers.");
return;
}
if (homePrice <= 0 || loanTermYears <= 0) {
alert("Home Price and Loan Term must be greater than zero.");
return;
}
// 3. Calculation Logic
var principal = homePrice – downPayment;
if (principal <= 0) {
alert("Down payment cannot be greater than or equal to the home price.");
return;
}
var monthlyRate = annualRate / 100 / 12;
var totalPayments = loanTermYears * 12;
var monthlyPayment = 0;
// Handle zero interest rate edge case
if (annualRate === 0) {
monthlyPayment = principal / totalPayments;
} else {
// Standard Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
monthlyPayment = principal * ( (monthlyRate * Math.pow(1 + monthlyRate, totalPayments)) / (Math.pow(1 + monthlyRate, totalPayments) – 1) );
}
var totalCost = monthlyPayment * totalPayments;
var totalInterest = totalCost – principal;
// 4. Update UI
// Format as Currency USD
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById('mc-monthly-payment').innerText = formatter.format(monthlyPayment);
document.getElementById('mc-total-principal').innerText = formatter.format(principal);
document.getElementById('mc-total-interest').innerText = formatter.format(totalInterest);
document.getElementById('mc-total-cost').innerText = formatter.format(totalCost);
// Show results section
document.getElementById('mc-results').style.display = 'block';
// Scroll to results slightly
document.getElementById('mc-results').scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}