Please enter valid numeric values greater than zero for Home Price and Loan Term.
Monthly Payment Breakdown
Principal & Interest:$0.00
Property Tax:$0.00
Homeowner's Insurance:$0.00
HOA Fees:$0.00
Total Monthly Payment:$0.00
Total Loan Amount:$0.00
Total Interest Paid (Over Life of Loan):$0.00
Payoff Date:—
Understanding Your Mortgage Payment
Buying a home is one of the largest financial decisions most people make. Using a mortgage calculator is an essential step in determining not just the price of the house you can buy, but the monthly payment you can realistically afford. Your monthly mortgage payment is typically composed of four main parts, often referred to as PITI:
Principal: The portion of your payment that goes toward paying down the loan balance.
Interest: The cost of borrowing the money, paid to the lender.
Taxes: Property taxes assessed by your local government, often held in escrow by your lender.
Insurance: Homeowners insurance to protect against damage, also typically held in escrow.
How Interest Rates Affect Affordability
Even a small difference in interest rates can have a significant impact on your monthly payment and the total cost of your loan. For example, on a $300,000 loan, a 1% increase in interest rate can raise your monthly payment by hundreds of dollars and cost you tens of thousands more over the life of a 30-year loan.
The Role of the Down Payment
Your down payment plays a crucial role in your mortgage structure. A larger down payment reduces the principal loan amount, which lowers your monthly payments. Additionally, if you put down less than 20% of the home's purchase price, you may be required to pay Private Mortgage Insurance (PMI), which is an extra monthly cost not calculated in the standard PITI but essential to consider.
30-Year vs. 15-Year Mortgages
The term of your loan affects both your monthly payment and the total interest paid. A 30-year fixed-rate mortgage offers lower monthly payments but results in paying more interest over time. A 15-year fixed-rate mortgage has higher monthly payments but allows you to build equity faster and save significantly on total interest costs.
How to Use This Calculator
To get the most accurate estimate:
Home Price: Enter the purchase price of the home.
Down Payment: Enter the cash amount you plan to pay upfront.
Loan Term: Choose the duration of the loan (commonly 15 or 30 years).
Interest Rate: Input the current annual interest rate offered by lenders.
Taxes & Insurance: Estimate annual property taxes and insurance premiums (check local listings for averages).
HOA Fees: If buying a condo or in a managed community, include monthly Homeowners Association fees.
function calculateMortgage() {
// 1. Get Input Values
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);
// 2. Validation
var errorDiv = document.getElementById("errorMsg");
var resultBox = document.getElementById("resultBox");
if (isNaN(homePrice) || isNaN(loanTerm) || homePrice <= 0 || loanTerm <= 0) {
errorDiv.style.display = "block";
resultBox.style.display = "none";
return;
} else {
errorDiv.style.display = "none";
resultBox.style.display = "block";
}
// Handle defaults for empty optional fields
if (isNaN(downPayment)) downPayment = 0;
if (isNaN(interestRate)) interestRate = 0;
if (isNaN(propertyTax)) propertyTax = 0;
if (isNaN(homeInsurance)) homeInsurance = 0;
if (isNaN(hoaFees)) hoaFees = 0;
// 3. Core Calculations
var principal = homePrice – downPayment;
var monthlyInterestRate = (interestRate / 100) / 12;
var numberOfPayments = loanTerm * 12;
var monthlyPrincipalInterest = 0;
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
if (interestRate === 0) {
monthlyPrincipalInterest = principal / numberOfPayments;
} else {
var mathPower = Math.pow(1 + monthlyInterestRate, numberOfPayments);
monthlyPrincipalInterest = principal * ((monthlyInterestRate * mathPower) / (mathPower – 1));
}
// Monthly Tax and Insurance
var monthlyTax = propertyTax / 12;
var monthlyInsurance = homeInsurance / 12;
// Total Monthly Payment
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance + hoaFees;
// Total Interest Calculation
var totalRepayment = monthlyPrincipalInterest * numberOfPayments;
var totalInterest = totalRepayment – principal;
// Payoff Date Estimate
var today = new Date();
var payoffYear = today.getFullYear() + loanTerm;
var payoffMonth = today.toLocaleString('default', { month: 'long' });
var payoffDateString = payoffMonth + " " + payoffYear;
// 4. Update UI
// Helper to format currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById("resPrincipalInterest").innerHTML = formatter.format(monthlyPrincipalInterest);
document.getElementById("resTax").innerHTML = formatter.format(monthlyTax);
document.getElementById("resInsurance").innerHTML = formatter.format(monthlyInsurance);
document.getElementById("resHOA").innerHTML = formatter.format(hoaFees);
document.getElementById("resTotal").innerHTML = formatter.format(totalMonthlyPayment);
document.getElementById("resLoanAmount").innerHTML = formatter.format(principal);
document.getElementById("resTotalInterest").innerHTML = formatter.format(totalInterest);
document.getElementById("resPayoffDate").innerHTML = payoffDateString;
}