function calculateMortgage() {
// Get Inputs
var homePrice = parseFloat(document.getElementById('homePrice').value);
var downPayment = parseFloat(document.getElementById('downPayment').value);
var loanTerm = parseFloat(document.getElementById('loanTerm').value);
var interestRate = parseFloat(document.getElementById('interestRate').value);
var propertyTax = parseFloat(document.getElementById('propertyTax').value);
var homeInsurance = parseFloat(document.getElementById('homeInsurance').value);
var hoaFees = parseFloat(document.getElementById('hoaFees').value);
// Validation
if (isNaN(homePrice) || homePrice <= 0) {
alert("Please enter a valid Home Price.");
return;
}
if (isNaN(downPayment)) downPayment = 0;
if (isNaN(interestRate) || interestRate < 0) interestRate = 0;
if (isNaN(propertyTax)) propertyTax = 0;
if (isNaN(homeInsurance)) homeInsurance = 0;
if (isNaN(hoaFees)) hoaFees = 0;
// Core Calculation Logic
var principal = homePrice – downPayment;
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = loanTerm * 12;
var monthlyPI = 0;
// Handle 0% interest edge case
if (interestRate === 0) {
monthlyPI = principal / numberOfPayments;
} else {
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
monthlyPI = principal * (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
}
var monthlyTax = propertyTax / 12;
var monthlyIns = homeInsurance / 12;
var totalMonthly = monthlyPI + monthlyTax + monthlyIns + hoaFees;
var totalInterest = (monthlyPI * numberOfPayments) – principal;
// Formatting Currency Function
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
// Output Results
document.getElementById('displayTotalMonthly').innerHTML = formatter.format(totalMonthly);
document.getElementById('displayPI').innerHTML = formatter.format(monthlyPI);
document.getElementById('displayTax').innerHTML = formatter.format(monthlyTax);
document.getElementById('displayIns').innerHTML = formatter.format(monthlyIns);
document.getElementById('displayHOA').innerHTML = formatter.format(hoaFees);
document.getElementById('displayPrincipal').innerHTML = formatter.format(principal);
document.getElementById('displayTotalInterest').innerHTML = formatter.format(totalInterest);
// Show Results Div
document.getElementById('mortgage-results').style.display = 'block';
}
Understanding Your Mortgage Payment Breakdown
Buying a home is one of the largest financial decisions you will ever make. While the listing price is a good starting point, it doesn't represent the true monthly cost of homeownership. This Mortgage Calculator is designed to help you estimate your total monthly payment by including critical factors often overlooked by basic calculators, such as property taxes, homeowner's insurance, and HOA fees.
What is PITI?
In the mortgage industry, your monthly payment is often referred to as PITI, which stands for:
Principal: The portion of your payment that goes toward paying down the loan balance ($).
Interest: The cost of borrowing money paid to the lender. In the early years of a mortgage, the majority of your payment goes toward interest.
Taxes: Property taxes assessed by your local government. These are typically held in an escrow account by your lender and paid annually on your behalf.
Insurance: Homeowners insurance protects your property against damage. Like taxes, this is usually bundled into your monthly payment via escrow.
How Interest Rates Affect Your Payment
Even a small change in interest rates can have a massive impact on your monthly payment and the total interest paid over the life of the loan. For example, on a $300,000 loan, a difference of just 1% in the interest rate can change your monthly payment by hundreds of dollars and your total interest cost by tens of thousands of dollars.
HOA Fees and Other Costs
If you are buying a condo or a home in a planned community, you will likely have to pay Homeowners Association (HOA) fees. These are paid directly to the association, not the lender, but they affect your debt-to-income ratio and monthly budget. Our calculator allows you to input these fees to get a realistic view of your monthly financial obligation.
Tips for Lowering Your Mortgage Payment
If the estimated payment is higher than your budget allows, consider these strategies:
Increase your down payment: This lowers the principal loan amount and reduces your monthly obligation.
Improve your credit score: A higher credit score can qualify you for lower interest rates.
Shop for insurance: Homeowners insurance rates vary significantly; shop around to find the best rate.
Consider a longer term: While a 15-year mortgage saves money on interest, a 30-year mortgage offers lower monthly payments.