Loan Summary:
Loan Amount:
Total Interest Paid:
Total Cost of Loan:
function calculateMortgage() {
// Get input values
var homePrice = parseFloat(document.getElementById("homePrice").value) || 0;
var downPayment = parseFloat(document.getElementById("downPayment").value) || 0;
var loanTermYears = parseInt(document.getElementById("loanTerm").value) || 30;
var interestRate = parseFloat(document.getElementById("interestRate").value) || 0;
var propertyTaxYear = parseFloat(document.getElementById("propertyTax").value) || 0;
var homeInsuranceYear = parseFloat(document.getElementById("homeInsurance").value) || 0;
var hoaFeesMonth = parseFloat(document.getElementById("hoaFees").value) || 0;
// Validation logic
if (homePrice <= 0) {
alert("Please enter a valid Home Price.");
return;
}
// 1. Calculate Loan Amount
var loanAmount = homePrice – downPayment;
if (loanAmount <= 0) {
alert("Down payment cannot be greater than or equal to Home Price.");
return;
}
// 2. Calculate Monthly Principal & Interest
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyInterestRate = (interestRate / 100) / 12;
var totalPayments = loanTermYears * 12;
var monthlyPI = 0;
if (interestRate === 0) {
monthlyPI = loanAmount / totalPayments;
} else {
var numerator = monthlyInterestRate * Math.pow((1 + monthlyInterestRate), totalPayments);
var denominator = Math.pow((1 + monthlyInterestRate), totalPayments) – 1;
monthlyPI = loanAmount * (numerator / denominator);
}
// 3. Calculate Monthly Components
var monthlyTax = propertyTaxYear / 12;
var monthlyInsurance = homeInsuranceYear / 12;
var totalMonthlyPayment = monthlyPI + monthlyTax + monthlyInsurance + hoaFeesMonth;
// 4. Calculate Totals
var totalAmountPaid = (monthlyPI * totalPayments);
var totalInterestPaid = totalAmountPaid – loanAmount;
// 5. Display Results
document.getElementById("resPrincipalInterest").innerText = formatCurrency(monthlyPI);
document.getElementById("resTax").innerText = formatCurrency(monthlyTax);
document.getElementById("resInsurance").innerText = formatCurrency(monthlyInsurance);
document.getElementById("resHOA").innerText = formatCurrency(hoaFeesMonth);
document.getElementById("resTotal").innerText = formatCurrency(totalMonthlyPayment);
document.getElementById("resLoanAmount").innerText = formatCurrency(loanAmount);
document.getElementById("resTotalInterest").innerText = formatCurrency(totalInterestPaid);
document.getElementById("resTotalCost").innerText = formatCurrency(totalAmountPaid + (monthlyTax * totalPayments) + (monthlyInsurance * totalPayments) + (hoaFeesMonth * totalPayments)); // Total cost including escrow over life
// Show result container
document.getElementById("resultsArea").style.display = "block";
}
function formatCurrency(num) {
return "$" + num.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}
Understanding Your Mortgage Payment
Buying a home is one of the largest financial decisions you will make. This Mortgage Calculator is designed to provide a comprehensive breakdown of your monthly financial obligations. Unlike simple calculators that only look at principal and interest, this tool factors in property taxes, homeowner's insurance, and HOA fees to give you a realistic "PITI" (Principal, Interest, Taxes, Insurance) estimate.
Components of a Monthly Mortgage Payment
Principal: The portion of your payment that goes toward paying down the loan balance ($350,000 house – $70,000 down = $280,000 principal).
Interest: The cost of borrowing money from the lender. In the early years of a mortgage, the majority of your payment goes toward interest.
Property Taxes: Taxes assessed by your local government, often bundled into your monthly payment through an escrow account.
Homeowners Insurance: Protects your property against damage. Lenders require this coverage.
HOA Fees: If you buy a condo or a home in a planned community, you may pay monthly Homeowners Association dues.
How Interest Rates Affect Your Payment
Even a small difference in interest rates can significantly impact your monthly payment and the total cost of your loan. For example, on a $300,000 loan, the difference between a 6.0% and 7.0% interest rate can change your monthly payment by nearly $200 and cost you tens of thousands of dollars over the life of a 30-year loan.
How to Use This Calculator
To get the most accurate result, gather your financial details before starting:
Enter Home Price: The purchase price of the property.
Input Down Payment: The cash amount you are paying upfront. A higher down payment reduces your loan amount and monthly payment.
Select Loan Term: Most buyers choose 30 years for lower monthly payments, while a 15-year term saves significantly on interest.
Add Escrow Details: Estimate your annual property tax and insurance costs. If unknown, 1.2% of the home price is a common estimate for taxes in the US.
Frequently Asked Questions
What is an amortization schedule?
An amortization schedule is a table detailing each periodic payment on an amortizing loan. It shows the amount of principal and interest that comprise each payment until the loan is paid off at the end of its term.
Should I choose a 15-year or 30-year mortgage?
A 15-year mortgage typically offers a lower interest rate and allows you to pay off the home faster, saving huge amounts on interest. However, the monthly payments are significantly higher than a 30-year mortgage, which offers lower monthly payments but costs more in the long run.