Please enter valid positive numbers for all fields.
Monthly Payment: $0.00
Principal & Interest:$0.00
Monthly Property Tax:$0.00
Monthly Home Insurance:$0.00
Total Loan Amount:$0.00
Total Interest Paid:$0.00
Total Cost of Loan:$0.00
function calculateMortgage() {
// Clear error
var errorDiv = document.getElementById("errorMsg");
var resultDiv = document.getElementById("results");
errorDiv.style.display = "none";
resultDiv.style.display = "none";
// Get inputs
var homePrice = parseFloat(document.getElementById("homePrice").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var loanTerm = parseFloat(document.getElementById("loanTerm").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var propertyTax = parseFloat(document.getElementById("propertyTax").value);
var homeInsurance = parseFloat(document.getElementById("homeInsurance").value);
// Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(loanTerm) || isNaN(interestRate) ||
homePrice < 0 || downPayment < 0 || loanTerm <= 0 || interestRate < 0) {
errorDiv.style.display = "block";
return;
}
if (isNaN(propertyTax)) propertyTax = 0;
if (isNaN(homeInsurance)) homeInsurance = 0;
// Calculations
var principal = homePrice – downPayment;
if (principal <= 0) {
errorDiv.innerHTML = "Down payment cannot be greater than or equal to home price.";
errorDiv.style.display = "block";
return;
}
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = loanTerm * 12;
var monthlyPI = 0;
// Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
if (interestRate === 0) {
monthlyPI = principal / numberOfPayments;
} else {
monthlyPI = principal * ( (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1) );
}
var monthlyTax = propertyTax / 12;
var monthlyIns = homeInsurance / 12;
var totalMonthly = monthlyPI + monthlyTax + monthlyIns;
var totalPaymentOverLife = (monthlyPI * numberOfPayments);
var totalInterest = totalPaymentOverLife – principal;
var totalCost = totalPaymentOverLife + (propertyTax * loanTerm) + (homeInsurance * loanTerm);
// Update DOM
document.getElementById("totalMonthlyDisplay").innerHTML = "$" + totalMonthly.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("piDisplay").innerHTML = "$" + monthlyPI.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("taxDisplay").innerHTML = "$" + monthlyTax.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("insDisplay").innerHTML = "$" + monthlyIns.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("loanAmountDisplay").innerHTML = "$" + principal.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("totalInterestDisplay").innerHTML = "$" + totalInterest.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("totalCostDisplay").innerHTML = "$" + totalCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
resultDiv.style.display = "block";
}
Understanding Your Mortgage Calculation
Buying a home is one of the most significant financial decisions you will make in your lifetime. Understanding how your monthly mortgage payment is calculated is crucial for budgeting and long-term financial planning. This Mortgage Payment Calculator helps you estimate your monthly costs by factoring in the home price, down payment, interest rate, loan term, and additional costs like property taxes and homeowners insurance.
Components of a Mortgage Payment (PITI)
Mortgage payments are often referred to as PITI, which stands for Principal, Interest, Taxes, and Insurance. Here is a breakdown of these components:
Principal: This is the money that goes toward paying down the actual loan balance. In the early years of a mortgage, the principal portion of your payment is small, but it grows over time as the interest portion decreases.
Interest: This is the cost of borrowing money from the lender. The interest rate significantly impacts your monthly payment and the total cost of the loan over time.
Taxes: Property taxes are assessed by your local government and are usually calculated as a percentage of your home's assessed value. Lenders often collect this monthly and hold it in an escrow account to pay the bill when it's due.
Insurance: Homeowners insurance protects your property against damage. Like taxes, this is often paid monthly into an escrow account. If you put down less than 20%, you may also have to pay Private Mortgage Insurance (PMI), which protects the lender.
Factors Affecting Your Monthly Payment
1. Down Payment Amount
The down payment is the initial upfront payment you make when purchasing a home. The larger your down payment, the lower your loan amount (principal) will be. A down payment of 20% or more typically helps you avoid Private Mortgage Insurance (PMI) and secures a lower interest rate, reducing your monthly obligation.
2. Interest Rate
Your interest rate is determined by broader economic factors and your personal credit score. Even a fraction of a percentage point difference can result in thousands of dollars in savings (or extra costs) over the life of a 30-year loan. Maintaining a high credit score is the best way to secure a favorable rate.
3. Loan Term
The loan term is the length of time you have to repay the loan. The most common terms are 15 years and 30 years.
30-Year Fixed: Offers lower monthly payments but results in paying more interest over the life of the loan.
15-Year Fixed: Has higher monthly payments but allows you to build equity faster and pay significantly less in total interest.
How to Use This Calculator
To get the most accurate estimate, gather your financial documents and input realistic numbers:
Enter Home Price: The purchase price of the property.
Input Down Payment: The cash you plan to pay upfront.
Set Loan Term: Choose how many years the mortgage will last (usually 15 or 30).
Input Interest Rate: Check current market rates or get a pre-approval quote.
Add Taxes and Insurance: Estimate these annual costs based on the property location (typically 1-2% of home value for taxes).
Click "Calculate Payment" to see your estimated monthly breakdown and total interest costs.
Frequently Asked Questions
Does this calculator include HOA fees?
This standard calculator focuses on PITI. If you are buying a condo or a home in a community with a Homeowners Association, you should add the monthly HOA fee on top of the calculated total to get your full housing expense.
What is an amortization schedule?
An amortization schedule is a table detailing each periodic payment on a 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.