Please enter valid positive numbers for all fields.
Monthly Payment:$0.00
Principal & Interest:$0.00
Property Taxes:$0.00
Homeowners Insurance:$0.00
HOA Fees:$0.00
Total Loan Amount:$0.00
Total Interest Paid:$0.00
Payoff Date:–
Understanding Your Mortgage Payment
Calculating your monthly mortgage payment is a critical step in the home buying process. This calculator breaks down the "PITI" components—Principal, Interest, Taxes, and Insurance—to give you a realistic view of your monthly financial commitment. Unlike simple loan calculators, this tool accounts for HOA fees and annual costs to prevent budget surprises.
Key Factors Affecting Your Mortgage
Principal & Interest: This is the core of your loan repayment. The amount depends heavily on your Home Price, Down Payment, and Interest Rate. A higher down payment reduces the principal loan amount, thereby lowering monthly costs.
Interest Rate: Even a fraction of a percentage point difference can equate to tens of thousands of dollars over the life of a 30-year loan.
Property Taxes & Insurance: These are often held in an escrow account. This calculator estimates the monthly portion of these annual costs.
Loan Term: A 30-year term offers lower monthly payments but results in significantly higher total interest paid compared to a 15-year term.
How to Use This Calculator
To get the most accurate result, enter the full purchase price of the home and your planned down payment. Check your local listings for estimated property tax rates (often 1-2% of home value) and obtain a quote for homeowners insurance. If you are buying a condo or a home in a planned community, do not forget to include the monthly HOA fees, as these can significantly impact your debt-to-income ratio.
Principal vs. Interest Over Time
In the early years of a fixed-rate mortgage, the majority of your payment goes toward interest. As time passes, a larger portion is applied to the principal balance. This process, known as amortization, means you build equity slowly at first, but the pace accelerates as the loan matures.
// Set default date to current month
var today = new Date();
var monthStr = (today.getMonth() + 1).toString().padStart(2, '0');
var yearStr = today.getFullYear();
document.getElementById('startDate').value = yearStr + "-" + monthStr;
function calculateMortgage() {
// 1. Get Input Values
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 insuranceYear = parseFloat(document.getElementById('insurance').value);
var hoaFeesMonth = parseFloat(document.getElementById('hoaFees').value);
var startDateVal = document.getElementById('startDate').value;
// 2. Validation
var errorDiv = document.getElementById('errorMsg');
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) ||
isNaN(loanTermYears) || isNaN(propertyTaxYear) || isNaN(insuranceYear) ||
homePrice <= 0 || loanTermYears = home price
if (principal <= 0) {
principal = 0;
}
var monthlyInterestRate = (interestRate / 100) / 12;
var numberOfPayments = loanTermYears * 12;
// Calculate Monthly P&I
var monthlyPI = 0;
if (interestRate === 0) {
monthlyPI = principal / numberOfPayments;
} else {
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var numerator = principal * monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments);
var denominator = Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1;
monthlyPI = numerator / denominator;
}
// If principal is 0, PI is 0
if (principal === 0) {
monthlyPI = 0;
}
// Calculate Escrow components
var monthlyTax = propertyTaxYear / 12;
var monthlyIns = insuranceYear / 12;
// Adjust inputs if NaN (treated as 0 if empty)
if (isNaN(monthlyTax)) monthlyTax = 0;
if (isNaN(monthlyIns)) monthlyIns = 0;
if (isNaN(hoaFeesMonth)) hoaFeesMonth = 0;
var totalMonthlyPayment = monthlyPI + monthlyTax + monthlyIns + hoaFeesMonth;
// Total Stats
var totalCostPI = monthlyPI * numberOfPayments;
var totalInterest = totalCostPI – principal;
if (totalInterest < 0) totalInterest = 0; // Prevent negative interest if errors occur
// Calculate Payoff Date
var start = new Date(startDateVal + "-01"); // Add day to make valid
start.setMonth(start.getMonth() + numberOfPayments);
var options = { year: 'numeric', month: 'long' };
var payoffDateStr = start.toLocaleDateString('en-US', options);
// 4. Update DOM
document.getElementById('monthlyTotal').innerText = formatCurrency(totalMonthlyPayment);
document.getElementById('monthlyPI').innerText = formatCurrency(monthlyPI);
document.getElementById('monthlyTax').innerText = formatCurrency(monthlyTax);
document.getElementById('monthlyIns').innerText = formatCurrency(monthlyIns);
document.getElementById('monthlyHOA').innerText = formatCurrency(hoaFeesMonth);
document.getElementById('totalLoanAmount').innerText = formatCurrency(principal);
document.getElementById('totalInterest').innerText = formatCurrency(totalInterest);
document.getElementById('payoffDate').innerText = payoffDateStr;
document.getElementById('resultsArea').style.display = 'block';
}
function formatCurrency(num) {
return '$' + num.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}