Estimate your monthly house payments, interest, and payoff details.
$
$
%
Y
$
$
Total Monthly Payment
$0.00
(Includes Principal, Interest, Tax & Insurance)
Principal & Interest
$0.00
Total Interest Paid
$0.00
Loan Amount
$0.00
How a Mortgage Calculator Works
Understanding your mortgage payment is the first step to successful homeownership. This mortgage calculator uses the standard amortization formula to determine exactly how much you will pay the bank each month based on the price of the home, your down payment, and current interest rates.
The calculation is broken down into four main components, often referred to as PITI:
Principal: The portion of your payment that reduces the loan balance.
Interest: The cost of borrowing money, calculated based on your Annual Percentage Rate (APR).
Taxes: Property taxes charged by your local municipality, typically divided by 12 and collected monthly.
Insurance: Homeowners insurance premiums to protect your property against damage.
The Impact of Interest Rates and Term Length
Even a small difference in your interest rate can have a massive impact on the total cost of your home. For example, on a $300,000 loan, a 1% increase in interest rate can add hundreds of dollars to your monthly payment and tens of thousands of dollars to the total interest paid over 30 years.
Similarly, choosing a 15-year term instead of a 30-year term will increase your monthly payment significantly, but it will drastically reduce the total interest you pay to the lender, potentially saving you over $100,000 in the long run.
How to Use This Tool
To get the most accurate estimate, enter the total purchase price of the home and your planned down payment. Don't forget to estimate your annual property taxes and insurance costs, as these are often bundled into your monthly mortgage payment through an escrow account. If you are unsure of the tax rate, 1.2% of the home's value is a common national average estimate.
function calculateMortgage() {
// 1. Get Input Values
var price = parseFloat(document.getElementById("homePrice").value);
var down = parseFloat(document.getElementById("downPayment").value);
var rate = parseFloat(document.getElementById("interestRate").value);
var years = parseFloat(document.getElementById("loanTerm").value);
var taxYear = parseFloat(document.getElementById("propertyTax").value);
var insYear = parseFloat(document.getElementById("homeInsurance").value);
// 2. Validate Inputs
if (isNaN(price) || isNaN(down) || isNaN(rate) || isNaN(years)) {
alert("Please enter valid numbers for all required fields.");
return;
}
if (price <= 0 || years = price
if (loanAmount <= 0) {
document.getElementById("totalMonthly").innerText = "$0.00";
document.getElementById("monthlyPI").innerText = "$0.00";
document.getElementById("totalInterest").innerText = "$0.00";
document.getElementById("loanAmountResult").innerText = "$0.00";
document.getElementById("mortgageResult").classList.add("active");
return;
}
var monthlyRate = (rate / 100) / 12;
var totalMonths = years * 12;
var monthlyPI = 0;
// Amortization Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
if (rate === 0) {
monthlyPI = loanAmount / totalMonths;
} else {
monthlyPI = (loanAmount * monthlyRate * Math.pow(1 + monthlyRate, totalMonths)) / (Math.pow(1 + monthlyRate, totalMonths) – 1);
}
var monthlyTax = taxYear / 12;
var monthlyIns = insYear / 12;
var totalMonthlyPayment = monthlyPI + monthlyTax + monthlyIns;
var totalInterestPaid = (monthlyPI * totalMonths) – loanAmount;
// 4. Update UI
// Helper for currency formatting
var fmt = new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' });
document.getElementById("totalMonthly").innerText = fmt.format(totalMonthlyPayment);
document.getElementById("monthlyPI").innerText = fmt.format(monthlyPI);
document.getElementById("totalInterest").innerText = fmt.format(totalInterestPaid);
document.getElementById("loanAmountResult").innerText = fmt.format(loanAmount);
// Show results
document.getElementById("mortgageResult").classList.add("active");
}