Estimate your monthly payments, interest, and payoff date.
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Total Monthly Payment:$0.00
Principal & Interest:$0.00
Property Tax (Monthly):$0.00
Home Insurance (Monthly):$0.00
HOA Fees:$0.00
Total Interest Paid Over Loan:$0.00
Estimated Payoff Date:–
Understanding Your Mortgage Calculation
Purchasing a home is one of the most significant financial decisions you will make. This mortgage calculator helps you understand exactly where your money goes every month by breaking down the PITI (Principal, Interest, Taxes, and Insurance) components of your payment.
How Is Your Monthly Payment Calculated?
Your total monthly payment is composed of several distinct parts:
Principal: The portion of your payment that pays down the actual balance of the loan.
Interest: The cost of borrowing money from your lender, calculated based on your annual interest rate.
Taxes: Property taxes assessed by your local government, typically collected by your lender in escrow.
Insurance: Homeowners insurance to protect your property against damage, also typically paid via escrow.
HOA Fees: If you live in a managed community, Homeowners Association fees are usually paid separately but affect your monthly affordability.
The Impact of Interest Rates and Down Payments
Even a small difference in your interest rate can result in tens of thousands of dollars in savings (or extra costs) over the life of a 30-year loan. Similarly, a larger down payment reduces your principal loan amount, which lowers both your monthly payment and the total interest paid.
Why Use a Mortgage Calculator?
Before beginning your house hunt, it is crucial to determine your budget. Lenders look at your debt-to-income ratio to approve you for a loan amount, but that amount might not fit your personal monthly budget. Use this tool to experiment with different home prices, interest rates, and down payments to find a comfort zone that allows you to enjoy homeownership without financial stress.
function calculateMortgage() {
// Get Inputs
var homePrice = parseFloat(document.getElementById('mc-home-price').value);
var downPayment = parseFloat(document.getElementById('mc-down-payment').value);
var interestRate = parseFloat(document.getElementById('mc-interest-rate').value);
var loanTermYears = parseFloat(document.getElementById('mc-loan-term').value);
var yearlyTax = parseFloat(document.getElementById('mc-property-tax').value);
var yearlyInsurance = parseFloat(document.getElementById('mc-insurance').value);
var monthlyHOA = parseFloat(document.getElementById('mc-hoa').value);
// Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTermYears)) {
alert("Please enter valid numbers for the main fields.");
return;
}
// Set defaults for optional fields if empty/NaN
if (isNaN(yearlyTax)) yearlyTax = 0;
if (isNaN(yearlyInsurance)) yearlyInsurance = 0;
if (isNaN(monthlyHOA)) monthlyHOA = 0;
// Core Calculation Logic
var principal = homePrice – downPayment;
// Prevent negative principal
if (principal <= 0) {
alert("Down payment cannot be greater than or equal to Home Price.");
return;
}
var monthlyRate = (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 {
var x = Math.pow(1 + monthlyRate, numberOfPayments);
monthlyPrincipalInterest = (principal * x * monthlyRate) / (x – 1);
}
var monthlyTax = yearlyTax / 12;
var monthlyInsurance = yearlyInsurance / 12;
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance + monthlyHOA;
var totalAmountPaid = monthlyPrincipalInterest * numberOfPayments;
var totalInterestPaid = totalAmountPaid – principal;
// Calculate Payoff Date
var today = new Date();
var payoffYear = today.getFullYear() + loanTermYears;
var payoffMonthStr = today.toLocaleString('default', { month: 'long' });
var payoffDateString = payoffMonthStr + " " + payoffYear;
// Update DOM
document.getElementById('res-total-monthly').innerHTML = "$" + totalMonthlyPayment.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-principal-interest').innerHTML = "$" + monthlyPrincipalInterest.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-tax-monthly').innerHTML = "$" + monthlyTax.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-insurance-monthly').innerHTML = "$" + monthlyInsurance.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-hoa-display').innerHTML = "$" + monthlyHOA.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-total-interest').innerHTML = "$" + totalInterestPaid.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-payoff-date').innerHTML = payoffDateString;
// Show Results
document.getElementById('mc-results').style.display = 'block';
}