Calculating a mortgage payment involves more than just repaying the bank for the loan amount. To get a realistic picture of your monthly financial obligation, you must consider the "PITI" components: Principal, Interest, Taxes, and Insurance.
What is Included in This Calculator?
Principal & Interest: The core repayment of your loan balance and the cost of borrowing money.
Property Taxes: Local government taxes based on the assessed value of your home, usually divided into monthly escrow payments.
Homeowners Insurance: Protection for your property against damage, required by lenders.
PMI (Private Mortgage Insurance): Required if your down payment is less than 20% of the home price.
HOA Dues: Fees paid to a Homeowners Association for community maintenance, which affects your total monthly housing cost.
How Interest Rates Affect Buying Power
Even a small fluctuation in interest rates can significantly impact your monthly payment and total loan cost. For example, on a $300,000 loan, a 1% increase in interest rate can raise your monthly payment by hundreds of dollars and cost tens of thousands more over the life of a 30-year loan. Use this tool to test different rate scenarios before locking in a loan.
The Importance of the Down Payment
Your down payment determines your Loan-to-Value (LTV) ratio. If you put down 20% or more, you typically avoid paying PMI. This calculator automatically adjusts the loan amount based on your entered down payment, allowing you to see exactly how much cash upfront is needed to reach your desired monthly budget.
function calculateMortgage() {
// 1. 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 loanTermYears = parseInt(document.getElementById("loanTerm").value);
var annualTax = parseFloat(document.getElementById("propertyTax").value);
var annualInsurance = parseFloat(document.getElementById("homeInsurance").value);
var pmiRate = parseFloat(document.getElementById("pmiRate").value);
var hoaDues = parseFloat(document.getElementById("hoaDues").value);
// 2. Validate Inputs
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTermYears)) {
alert("Please enter valid numbers for Home Price, Down Payment, Rate, and Term.");
return;
}
// 3. Core Calculations
var loanAmount = homePrice – downPayment;
// Handle case where down payment >= home price
if (loanAmount 80%
var monthlyPMI = 0;
var ltv = (loanAmount / homePrice) * 100;
if (ltv > 80 && pmiRate > 0) {
monthlyPMI = (loanAmount * (pmiRate / 100)) / 12;
}
// Total Monthly Payment
var totalMonthly = monthlyPI + monthlyTax + monthlyInsurance + monthlyPMI + hoaDues;
// Total Interest over life of loan
var totalCostOfLoan = monthlyPI * totalPayments;
var totalInterest = totalCostOfLoan – loanAmount;
// 4. Display Results
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById("resultsSection").style.display = "block";
document.getElementById("totalMonthlyPayment").innerHTML = formatter.format(totalMonthly);
document.getElementById("piPayment").innerHTML = formatter.format(monthlyPI);
document.getElementById("taxPayment").innerHTML = formatter.format(monthlyTax);
document.getElementById("insPayment").innerHTML = formatter.format(monthlyInsurance);
document.getElementById("pmiPayment").innerHTML = formatter.format(monthlyPMI);
document.getElementById("loanAmountResult").innerHTML = formatter.format(loanAmount);
document.getElementById("totalInterestResult").innerHTML = formatter.format(totalInterest);
}