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);
// Validation
if (isNaN(homePrice) || homePrice <= 0) {
alert("Please enter a valid Home Price.");
return;
}
if (isNaN(downPayment) || downPayment < 0) {
downPayment = 0;
}
if (isNaN(interestRate) || interestRate = home price
if (principal <= 0) {
document.getElementById('resPrincipalInterest').innerText = "$0.00";
document.getElementById('resTax').innerText = "$" + (propertyTax / 12).toFixed(2);
document.getElementById('resInsurance').innerText = "$" + (homeInsurance / 12).toFixed(2);
document.getElementById('resHOA').innerText = "$" + hoaFees.toFixed(2);
var totalZeroLoan = (propertyTax / 12) + (homeInsurance / 12) + hoaFees;
document.getElementById('resTotal').innerText = "$" + totalZeroLoan.toFixed(2);
document.getElementById('result').style.display = 'block';
return;
}
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = loanTerm * 12;
// Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPrincipalInterest = 0;
if (interestRate === 0) {
monthlyPrincipalInterest = principal / numberOfPayments;
} else {
var mathPower = Math.pow(1 + monthlyRate, numberOfPayments);
monthlyPrincipalInterest = principal * ((monthlyRate * mathPower) / (mathPower – 1));
}
var monthlyTax = propertyTax / 12;
var monthlyInsurance = homeInsurance / 12;
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance + hoaFees;
// Update UI
document.getElementById('resPrincipalInterest').innerText = "$" + monthlyPrincipalInterest.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resTax').innerText = "$" + monthlyTax.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resInsurance').innerText = "$" + monthlyInsurance.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resHOA').innerText = "$" + hoaFees.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resTotal').innerText = "$" + totalMonthlyPayment.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('result').style.display = 'block';
}
Understanding Your Monthly Mortgage Payment
Purchasing 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 stability. This Mortgage Payment Calculator helps you estimate your monthly housing costs by factoring in principal, interest, taxes, insurance, and HOA fees.
Components of a Mortgage Payment
Your monthly payment is typically referred to as PITI (Principal, Interest, Taxes, and Insurance). Here is a breakdown of what each component means for your wallet:
Principal: This is the money that goes directly toward paying down the loan balance. In the early years of a mortgage, the principal portion of your payment is small, but it grows over time as you pay off interest.
Interest: This is the cost of borrowing money from the lender. The interest rate significantly impacts your monthly payment. A higher rate means you pay more in interest over the life of the loan.
Property Taxes: Local governments assess taxes on property to fund public services like schools and roads. Lenders often collect this monthly and hold it in an escrow account to pay the tax bill when it is due.
Homeowners Insurance: This protects your home against damage from fires, storms, and other hazards. Like property taxes, this is often paid via an escrow account.
How Interest Rates Affect Affordability
Even a small fluctuation in interest rates can drastically change your monthly payment and the total cost of the loan. For example, on a $300,000 loan, a 1% difference in the interest rate can change your monthly payment by hundreds of dollars and your total interest paid by tens of thousands of dollars over 30 years.
The Impact of the Loan Term
The loan term is the length of time you have to repay the loan. The most common terms are:
30-Year Fixed: Offers lower monthly payments but results in higher total interest costs over the life of the loan.
15-Year Fixed: Comes with higher monthly payments but allows you to build equity faster and pay significantly less in total interest.
Don't Forget HOA Fees
If you are buying a condo or a home in a planned community, you may be required to pay Homeowners Association (HOA) fees. These fees cover common area maintenance, amenities, and sometimes utilities. While HOA fees are usually paid directly to the association, lenders factor them into your debt-to-income ratio when qualifying you for a loan. Our calculator allows you to include these fees to get a true picture of your monthly obligation.
Using This Calculator for Budgeting
To use this calculator effectively, start by estimating the home price you are comfortable with. Input your planned down payment—remembering that a down payment of less than 20% often requires Private Mortgage Insurance (PMI), which increases costs (you can add estimated PMI to the "Yearly Home Insurance" field or adjust your budget). By adjusting the variables, you can see how different home prices, interest rates, and down payments impact your bottom line.