Please enter valid numeric values for all required fields.
Estimated Payment: /mo
Principal & Interest
Property Tax (Monthly)
Homeowner's Insurance
HOA Fees
Total Monthly Payment
function calculateMortgage() {
// Retrieve inputs
var homePrice = document.getElementById('homePrice').value;
var downPayment = document.getElementById('downPayment').value;
var loanTerm = document.getElementById('loanTerm').value;
var interestRate = document.getElementById('interestRate').value;
var propertyTax = document.getElementById('propertyTax').value;
var homeInsurance = document.getElementById('homeInsurance').value;
var hoaFees = document.getElementById('hoaFees').value;
// Validation logic
if (homePrice === "" || downPayment === "" || loanTerm === "" || interestRate === "" || propertyTax === "" || homeInsurance === "") {
document.getElementById('errorMsg').style.display = 'block';
document.getElementById('calcResults').style.display = 'none';
return;
}
// Parse numbers
var price = parseFloat(homePrice);
var down = parseFloat(downPayment);
var termYears = parseFloat(loanTerm);
var annualRate = parseFloat(interestRate);
var annualTax = parseFloat(propertyTax);
var annualIns = parseFloat(homeInsurance);
var monthlyHOA = hoaFees === "" ? 0 : parseFloat(hoaFees);
// Check for non-numeric values
if (isNaN(price) || isNaN(down) || isNaN(termYears) || isNaN(annualRate) || isNaN(annualTax) || isNaN(annualIns)) {
document.getElementById('errorMsg').style.display = 'block';
return;
}
document.getElementById('errorMsg').style.display = 'none';
// Calculation Logic
var principal = price – down;
var monthlyRate = (annualRate / 100) / 12;
var numberOfPayments = termYears * 12;
var monthlyPI = 0;
// Handle zero interest rate edge case
if (annualRate === 0) {
monthlyPI = principal / numberOfPayments;
} else {
// Standard Amortization 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 = annualTax / 12;
var monthlyIns = annualIns / 12;
var totalPayment = monthlyPI + monthlyTax + monthlyIns + monthlyHOA;
// Update DOM
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById('displayPI').innerText = formatter.format(monthlyPI);
document.getElementById('displayTax').innerText = formatter.format(monthlyTax);
document.getElementById('displayIns').innerText = formatter.format(monthlyIns);
document.getElementById('displayHOA').innerText = formatter.format(monthlyHOA);
document.getElementById('displayTotal').innerText = formatter.format(totalPayment);
document.getElementById('displayTotalBottom').innerText = formatter.format(totalPayment);
document.getElementById('calcResults').style.display = 'block';
}
Understanding Your Monthly Mortgage Payment
Buying a home is one of the largest financial decisions you will make. While the listing price of a home gives you a general idea of the cost, your actual monthly obligation involves several other critical factors. This Mortgage Payment Calculator is designed to give you a comprehensive view of what your monthly check will actually look like by factoring in Principal, Interest, Taxes, and Insurance (often referred to as PITI).
The 4 Pillars of a Mortgage Payment (PITI)
When you take out a mortgage loan, your monthly payment covers more than just paying back the money you borrowed. Here is a breakdown of the components:
Principal: This is the portion of your payment that goes directly toward reducing the outstanding balance of your loan. In the early years of a 30-year mortgage, the principal portion is small, but it grows over time.
Interest: This is the cost of borrowing money. With a fixed-rate mortgage, your interest rate stays the same, but the amount of interest you pay decreases as your principal balance goes down.
Taxes: Property taxes are assessed by your local government to fund schools, roads, and emergency services. These are typically collected by your lender in an escrow account and paid annually on your behalf.
Insurance: Homeowner's insurance protects your property against hazards like fire and theft. Lenders require this coverage to protect their investment in your home.
How Interest Rates Impact Affordability
Even a small fluctuation in interest rates can significantly impact your buying power. For example, on a $300,000 loan, the difference between a 4.0% and a 5.0% interest rate can change your monthly payment by over $180. Over the life of a 30-year loan, that 1% difference costs you nearly $65,000 in additional interest payments.
Example Calculation
Let's say you are looking to purchase a home for $350,000. You have saved a 20% down payment ($70,000), meaning you need to finance $280,000.
Loan Term: 30 Years
Interest Rate: 6.5%
Annual Property Tax: $4,000
Annual Insurance: $1,200
Using the calculator above, your base Principal & Interest payment would be approximately $1,770. However, once you add in the taxes ($333/mo) and insurance ($100/mo), your total monthly obligation rises to roughly $2,203. Being aware of this "all-in" number helps prevent financial strain after closing.
Don't Forget HOA Fees
If you are buying a condo or a home in a planned community, you likely have Homeowners Association (HOA) fees. While these are usually paid directly to the association rather than your mortgage lender, they are a mandatory monthly cost that reduces your mortgage qualification amount. Always input these fees into the calculator to get the most accurate picture of your housing budget.