Purchasing a home is one of the most significant financial decisions you will make. This Mortgage Payment Calculator helps you estimate your monthly payments by factoring in the home price, down payment, interest rate, and loan term. It also accounts for property taxes, homeowners insurance, and HOA fees to give you a realistic view of your "PITI" (Principal, Interest, Taxes, and Insurance) costs.
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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 (Life of Loan):$0.00
Understanding Your Mortgage Breakdown
When you calculate your mortgage payment, it is essential to look beyond the principal and interest. Lenders often look at the PITI calculation to determine your ability to repay the loan.
Principal and Interest (P&I)
This is the core component of your mortgage. Principal pays down the loan balance, while Interest is the cost of borrowing that money. Early in your loan term, the majority of your payment goes toward interest. Over time, more goes toward the principal.
Taxes and Insurance (Escrow)
Most lenders require you to pay 1/12th of your annual property taxes and homeowners insurance premiums with your monthly mortgage payment. These funds are held in an escrow account and paid on your behalf when due.
How Interest Rates Impact Affordability
Even a small difference in interest rates can significantly affect your monthly payment and the total interest paid over the life of the loan. For example, on a $300,000 loan, a 1% increase in interest rate can increase your monthly payment by hundreds of dollars and your total interest cost by tens of thousands.
function calculateMortgage() {
// 1. Get 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 propertyTaxYear = parseFloat(document.getElementById("propertyTax").value);
var homeInsuranceYear = parseFloat(document.getElementById("homeInsurance").value);
var hoaFeesMonth = parseFloat(document.getElementById("hoaFees").value);
// 2. Validate Inputs
var errorMsg = document.getElementById("errorMsg");
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTermYears) ||
homePrice < 0 || downPayment < 0 || interestRate < 0) {
errorMsg.style.display = "block";
document.getElementById("resultsSection").style.display = "none";
return;
} else {
errorMsg.style.display = "none";
}
// Handle empty optional fields with 0
if (isNaN(propertyTaxYear)) propertyTaxYear = 0;
if (isNaN(homeInsuranceYear)) homeInsuranceYear = 0;
if (isNaN(hoaFeesMonth)) hoaFeesMonth = 0;
// 3. Calculation Logic
var loanAmount = homePrice – downPayment;
// Edge case: if downpayment is greater than price
if (loanAmount < 0) loanAmount = 0;
var monthlyRate = (interestRate / 100) / 12;
var totalPayments = loanTermYears * 12;
var monthlyPI = 0;
// Standard Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
if (interestRate === 0) {
monthlyPI = loanAmount / totalPayments;
} else {
monthlyPI = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, totalPayments)) / (Math.pow(1 + monthlyRate, totalPayments) – 1);
}
// Calculate monthly portions of annual costs
var monthlyTax = propertyTaxYear / 12;
var monthlyInsurance = homeInsuranceYear / 12;
// Total Monthly Payment
var totalMonthly = monthlyPI + monthlyTax + monthlyInsurance + hoaFeesMonth;
// Total Interest Paid over life of loan
var totalCostOfLoan = (monthlyPI * totalPayments);
var totalInterest = totalCostOfLoan – loanAmount;
// 4. Update UI
// Helper to format currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById("totalMonthlyPayment").innerHTML = formatter.format(totalMonthly);
document.getElementById("piPayment").innerHTML = formatter.format(monthlyPI);
document.getElementById("taxMonthly").innerHTML = formatter.format(monthlyTax);
document.getElementById("insMonthly").innerHTML = formatter.format(monthlyInsurance);
document.getElementById("hoaResult").innerHTML = formatter.format(hoaFeesMonth);
document.getElementById("loanAmountResult").innerHTML = formatter.format(loanAmount);
document.getElementById("totalInterest").innerHTML = formatter.format(totalInterest);
// Show results container
document.getElementById("resultsSection").style.display = "block";
}