Total Loan Amount: $0.00
Total Interest Paid over Life of Loan: $0.00
function calculateMortgage() {
// Get Input Values
var price = parseFloat(document.getElementById('homePrice').value);
var down = parseFloat(document.getElementById('downPayment').value);
var termYears = parseFloat(document.getElementById('loanTerm').value);
var ratePercent = parseFloat(document.getElementById('interestRate').value);
var annualTax = parseFloat(document.getElementById('propertyTax').value);
var annualIns = parseFloat(document.getElementById('homeInsurance').value);
var monthlyHOA = parseFloat(document.getElementById('hoaFees').value);
// Validation
if (isNaN(price) || isNaN(down) || isNaN(termYears) || isNaN(ratePercent)) {
alert("Please enter valid numbers for Price, Down Payment, Term, and Rate.");
return;
}
// Handle optional fields as 0 if empty/NaN
if (isNaN(annualTax)) annualTax = 0;
if (isNaN(annualIns)) annualIns = 0;
if (isNaN(monthlyHOA)) monthlyHOA = 0;
// Calculations
var loanAmount = price – down;
var monthlyRate = ratePercent / 100 / 12;
var numPayments = termYears * 12;
var monthlyPI = 0;
// Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
if (monthlyRate === 0) {
monthlyPI = loanAmount / numPayments;
} else {
monthlyPI = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numPayments)) / (Math.pow(1 + monthlyRate, numPayments) – 1);
}
var monthlyTax = annualTax / 12;
var monthlyIns = annualIns / 12;
var totalMonthlyPayment = monthlyPI + monthlyTax + monthlyIns + monthlyHOA;
var totalCost = monthlyPI * numPayments;
var totalInterest = totalCost – loanAmount;
// Display Results
document.getElementById('resPI').innerText = "$" + monthlyPI.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resTax').innerText = "$" + monthlyTax.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resIns').innerText = "$" + monthlyIns.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resHOA').innerText = "$" + monthlyHOA.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resTotal').innerText = "$" + totalMonthlyPayment.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resLoanAmount').innerText = "$" + loanAmount.toLocaleString('en-US', {minimumFractionDigits: 0, maximumFractionDigits: 0});
document.getElementById('resTotalInterest').innerText = "$" + totalInterest.toLocaleString('en-US', {minimumFractionDigits: 0, maximumFractionDigits: 0});
// Show result box
document.getElementById('results').style.display = "block";
}
Understanding Your PITI Mortgage Payment
When planning to purchase a home, many buyers focus solely on the principal and interest portion of their mortgage. However, your actual monthly financial obligation typically includes four key components, known collectively as PITI: Principal, Interest, Taxes, and Insurance.
Using a PITI Mortgage Calculator gives you a much more realistic view of affordability than a standard loan calculator. By factoring in property taxes, homeowners insurance, and even HOA fees, you can avoid "payment shock" when the first bill arrives.
1. Principal
The principal is the amount of money you borrowed from the lender to buy the home. This is calculated as the home price minus your down payment. In the early years of a standard 30-year fixed mortgage, a very small percentage of your payment goes toward principal, while the majority pays off interest.
2. Interest
Interest is the fee the lender charges you for borrowing the money. Your interest rate is determined by the broader economic environment and your personal credit score. Even a difference of 0.5% in your interest rate can result in tens of thousands of dollars in savings (or extra costs) over the life of the loan.
3. Taxes
Property taxes are levied by your local government to fund public services like schools, roads, and police departments. These are typically assessed annually based on the value of your property. Lenders often collect 1/12th of your annual tax bill each month and hold it in an escrow account to pay the government on your behalf.
4. Insurance
Homeowners insurance protects your property against damage from fire, theft, and other disasters. Like taxes, lenders usually require you to pay this monthly into an escrow account. If you put down less than 20% on your home, you may also be required to pay Private Mortgage Insurance (PMI), which protects the lender if you default.
The Impact of HOA Fees
While not part of the standard PITI acronym, Homeowners Association (HOA) fees are a critical factor for condos, townhomes, and planned communities. These fees cover common area maintenance and amenities. Our calculator includes an input for HOA fees because they are a mandatory monthly cost that affects your debt-to-income ratio and overall affordability.
How to Lower Your Monthly Payment
Increase your down payment: This reduces the principal loan amount and may eliminate the need for PMI.
Shop for lower insurance rates: Bundling home and auto insurance can often yield discounts.
Challenge your property tax assessment: If you believe your home's assessed value is too high compared to neighbors, you can file an appeal with your local county.
Improve your credit score: A higher score helps you qualify for lower interest rates.
Use the calculator above to experiment with different scenarios. Seeing how a larger down payment or a slightly lower interest rate impacts your total monthly outlay can help you make a smarter home-buying decision.