Estimate your monthly payments, including taxes and insurance.
30 Years
20 Years
15 Years
10 Years
Please enter valid positive numbers for all fields.
Estimated Monthly Payment
$0.00
Principal & Interest:$0.00
Property Tax (Monthly):$0.00
Home Insurance (Monthly):$0.00
HOA Fees:$0.00
Total Loan Amount:$0.00
Total Interest Paid:$0.00
Payoff Date:–
function calculateMortgage() {
// Retrieve inputs
var homePrice = parseFloat(document.getElementById("homePrice").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTermYears = parseInt(document.getElementById("loanTerm").value);
var propertyTaxAnnual = parseFloat(document.getElementById("propertyTax").value);
var homeInsuranceAnnual = parseFloat(document.getElementById("homeInsurance").value);
var hoaFeesMonthly = parseFloat(document.getElementById("hoaFees").value);
var errorMsg = document.getElementById("errorMessage");
var resultsBox = document.getElementById("results");
// Validate inputs
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTermYears) ||
isNaN(propertyTaxAnnual) || isNaN(homeInsuranceAnnual) || isNaN(hoaFeesMonthly) ||
homePrice < 0 || downPayment < 0 || interestRate < 0 || loanTermYears <= 0) {
errorMsg.style.display = "block";
resultsBox.style.display = "none";
return;
} else {
errorMsg.style.display = "none";
}
// Logic
var principal = homePrice – downPayment;
if (principal <= 0) {
alert("Down payment cannot equal or exceed home price.");
return;
}
var monthlyInterestRate = (interestRate / 100) / 12;
var numberOfPayments = loanTermYears * 12;
// Amortization Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPrincipalInterest = 0;
if (interestRate === 0) {
monthlyPrincipalInterest = principal / numberOfPayments;
} else {
monthlyPrincipalInterest = principal *
(monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) /
(Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
}
var monthlyTax = propertyTaxAnnual / 12;
var monthlyInsurance = homeInsuranceAnnual / 12;
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance + hoaFeesMonthly;
var totalCostOfLoan = (monthlyPrincipalInterest * numberOfPayments);
var totalInterestPaid = totalCostOfLoan – principal;
// Date Calculation
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();
// Formatter
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
// Display Results
document.getElementById("displayTotalMonthly").innerHTML = formatter.format(totalMonthlyPayment);
document.getElementById("displayPrincipalInterest").innerHTML = formatter.format(monthlyPrincipalInterest);
document.getElementById("displayTax").innerHTML = formatter.format(monthlyTax);
document.getElementById("displayInsurance").innerHTML = formatter.format(monthlyInsurance);
document.getElementById("displayHOA").innerHTML = formatter.format(hoaFeesMonthly);
document.getElementById("displayLoanAmount").innerHTML = formatter.format(principal);
document.getElementById("displayTotalInterest").innerHTML = formatter.format(totalInterestPaid);
document.getElementById("displayPayoffDate").innerHTML = payoffString;
resultsBox.style.display = "block";
}
Understanding Your Mortgage Calculator Results
Using a mortgage calculator is the first step in determining your home buying budget. This tool breaks down your monthly obligations into distinct categories, ensuring you have a clear picture of the true cost of homeownership beyond just the listing price.
How is the Monthly Mortgage Payment Calculated?
Your monthly payment is composed of four main parts, often referred to as PITI (Principal, Interest, Taxes, and Insurance):
Principal: The portion of your payment that goes directly toward reducing your loan balance.
Interest: The cost of borrowing money from your lender, calculated as a percentage of the remaining principal.
Taxes: Property taxes charged by your local government, usually held in an escrow account by your lender.
Insurance: Homeowners insurance protects your property against damage. Lenders require this to protect their investment.
Why Include HOA Fees?
If you are buying a condo or a home in a planned community, you will likely have to pay Homeowners Association (HOA) fees. While these are paid directly to the association and not your lender, they significantly impact your monthly affordability and Debt-to-Income (DTI) ratio.
The Impact of Interest Rates
Even a small difference in interest rates can have a massive impact on your total loan cost. For example, on a $300,000 loan, a 1% difference in interest rate can save or cost you tens of thousands of dollars over a 30-year term. Use this calculator to experiment with different rates to see how refinancing or buying down points might benefit you.
Frequently Asked Questions
What is a good down payment?
Traditionally, 20% is considered the gold standard as it allows you to avoid Private Mortgage Insurance (PMI). However, many buyers purchase homes with as little as 3% or 3.5% down depending on the loan program (Conventional vs. FHA).
Does this calculator include PMI?
This calculator focuses on PITI and HOA. If your down payment is less than 20%, you should budget an additional 0.5% to 1% of the loan amount annually for Private Mortgage Insurance until you reach 20% equity.
How accurate is the payoff date?
The payoff date assumes you make exactly the required payment every month for the full term of the loan. Making extra payments toward the principal can significantly shorten your loan term and reduce total interest paid.