Total Loan Amount: $0.00 |
Total Interest Cost: $0.00
function calculateMortgage() {
// 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 loanTerm = parseFloat(document.getElementById("loanTerm").value);
var propertyTax = parseFloat(document.getElementById("propertyTax").value);
var homeInsurance = parseFloat(document.getElementById("homeInsurance").value);
var hoaFees = parseFloat(document.getElementById("hoaFees").value);
var errorDiv = document.getElementById("errorMsg");
var resultsDiv = document.getElementById("resultsArea");
// Basic validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm) ||
isNaN(propertyTax) || isNaN(homeInsurance) || isNaN(hoaFees)) {
errorDiv.style.display = "block";
resultsDiv.style.display = "none";
return;
}
if (homePrice <= 0 || loanTerm <= 0) {
errorDiv.style.display = "block";
resultsDiv.style.display = "none";
return;
}
errorDiv.style.display = "none";
// Calculations
var loanAmount = homePrice – downPayment;
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = loanTerm * 12;
var monthlyPrincipalInterest = 0;
// Handle zero interest rate edge case
if (interestRate === 0) {
monthlyPrincipalInterest = loanAmount / numberOfPayments;
} else {
monthlyPrincipalInterest = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
}
var monthlyTax = propertyTax / 12;
var monthlyInsurance = homeInsurance / 12;
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance + hoaFees;
var totalInterest = (monthlyPrincipalInterest * numberOfPayments) – loanAmount;
// Formatting currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
});
// Update UI
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(loanAmount);
document.getElementById("resTotalInterest").innerHTML = formatter.format(totalInterest);
resultsDiv.style.display = "block";
}
Understanding Your Mortgage Payment Components
Buying a home is one of the most significant financial decisions you will ever make. While most people focus on the listing price of the house, the true affordability is determined by your monthly mortgage payment. This calculator provides a comprehensive breakdown of your estimated payments, known in the real estate industry as PITI (Principal, Interest, Taxes, and Insurance).
1. Principal and Interest
This is the core of your mortgage payment. The Principal is the money that goes toward paying down the loan balance, building your equity in the home. The Interest is the cost of borrowing that money from the lender. In the early years of a standard 30-year fixed-rate mortgage, the majority of your payment goes toward interest. As time passes, a larger portion shifts toward paying off the principal.
2. Property Taxes
Property taxes are assessed by your local government to fund public services like schools, roads, and police departments. Lenders typically collect this money from you in monthly installments (escrow) and pay the tax bill on your behalf at the end of the year. Our calculator estimates the monthly impact of your annual tax bill.
3. Homeowners Insurance & HOA Fees
Lenders require you to carry homeowners insurance to protect the asset against damage from fire, storms, or theft. Additionally, if you are buying a condo or a home in a planned community, you may be liable for Homeowners Association (HOA) fees. While HOA fees are usually paid directly to the association, they are a critical part of your monthly debt-to-income ratio.
How Interest Rates Affect Affordability
Even a small fluctuation in interest rates can drastically change your buying power. For example, on a $300,000 loan, a 1% increase in the interest rate can increase your monthly payment by hundreds of dollars and add tens of thousands of dollars to the total cost of the loan over 30 years. Using this calculator helps you visualize how different rates impact your budget.
Tips for Lowering Your Monthly Payment
Increase Your Down Payment: Putting more than 20% down avoids Private Mortgage Insurance (PMI) and lowers the principal loan amount.
Improve Your Credit Score: A higher credit score often qualifies you for lower interest rates.
Shop for Insurance: Homeowners insurance premiums vary wildly; get quotes from multiple providers.
Consider a 15-Year Term: While monthly payments are higher, the interest rate is usually lower, and you pay significantly less total interest.