function calculateMortgage() {
// 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);
// Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(loanTerm) || isNaN(interestRate)) {
alert("Please enter valid numbers for the primary fields (Home Price, Down Payment, Term, Rate).");
return;
}
// Defaults for optional fields
if (isNaN(propertyTax)) propertyTax = 0;
if (isNaN(homeInsurance)) homeInsurance = 0;
if (isNaN(hoaFees)) hoaFees = 0;
// Calculations
var principal = homePrice – downPayment;
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = loanTerm * 12;
var monthlyPI = 0;
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 monthlyInsurance = homeInsurance / 12;
var monthlyEscrow = monthlyTax + monthlyInsurance;
var totalMonthlyPayment = monthlyPI + monthlyEscrow + hoaFees;
// Update UI
document.getElementById("displayLoanAmount").innerText = "$" + principal.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("displayPI").innerText = "$" + monthlyPI.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("displayEscrow").innerText = "$" + monthlyEscrow.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("displayHOA").innerText = "$" + hoaFees.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("displayTotal").innerText = "$" + totalMonthlyPayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("results").style.display = "block";
}
Understanding Your Mortgage Calculation
Buying a home is often the largest financial commitment a person will make in their lifetime. Our Mortgage Payment Calculator helps you estimate your monthly financial obligations accurately. It breaks down the costs into Principal & Interest, Taxes, and Insurance, giving you a clear picture of affordability before you make an offer.
What Makes Up Your Monthly Mortgage Payment?
Your monthly payment is typically referred to as PITI (Principal, Interest, Taxes, and Insurance). Here is a breakdown of what these terms mean for your wallet:
Principal: This is the money that goes directly toward paying down the loan balance. In the early years of a mortgage, a smaller portion of your payment goes to principal.
Interest: This is the cost of borrowing money from the lender. Initially, this makes up the bulk of your payment. The rate is determined by market conditions and your credit score.
Property Taxes: Local governments assess these taxes to fund public services. They are usually calculated as a percentage of your home's assessed value and can add significantly to your monthly costs.
Homeowners Insurance: Lenders require insurance to protect the property against damage. This is often bundled into your monthly payment via an escrow account.
HOA Fees: If you buy a condo or a home in a managed community, you may have Homeowners Association fees. While these aren't paid to the lender, they affect your total monthly housing budget.
How Interest Rates Affect Your Buying Power
Even a small fluctuation in interest rates can dramatically change your monthly payment and the total cost of the loan over time. For example, on a $400,000 loan, a difference of just 1% in the interest rate can change your monthly payment by hundreds of dollars and your total interest paid over 30 years by nearly $100,000.
Tips for Lowering Your Mortgage Payments
If the calculated monthly payment is higher than your budget allows, consider these strategies:
Increase Your Down Payment: Putting more money down reduces the principal loan amount, which lowers your monthly P&I and may eliminate the need for Private Mortgage Insurance (PMI).
Improve Your Credit Score: A higher credit score often qualifies you for a lower interest rate.
Shop for Insurance: Homeowners insurance rates vary. Shopping around can save you money on your monthly escrow payments.
Consider a Different Term: While a 15-year mortgage saves interest in the long run, a 30-year mortgage offers lower monthly payments.
Using This Calculator for Refinancing
This tool is not just for new homebuyers. If you currently have a mortgage, you can use this calculator to see if refinancing at a lower rate would save you money. Simply input your current loan balance as the "Home Price" (with 0 down payment) or adjust the figures to match your refinancing loan amount to compare the new estimated payment against your current one.