Calculating your monthly mortgage payment is the first critical step in the home-buying process. While the sticker price of a home is important, the monthly obligation—often referred to as PITI (Principal, Interest, Taxes, and Insurance)—determines true affordability. Our specialized Mortgage Payment Calculator breaks down these costs to give you a realistic view of your financial commitment.
What is Included in PITI?
Most first-time homebuyers focus solely on the principal and interest, but a standard mortgage payment typically comprises four distinct parts:
Principal: The portion of your payment that goes toward paying down the loan balance. In the early years of a mortgage, this amount is small but grows over time.
Interest: The cost of borrowing money. With high interest rates, this can make up the majority of your payment for the first decade of a 30-year loan.
Taxes: Property taxes assessed by your local government. These are usually collected by the lender in an escrow account and paid annually on your behalf.
Insurance: Homeowners insurance protects the property against damage. Like taxes, this is often divided into monthly installments and held in escrow.
How Interest Rates Affect Your Buying Power
Even a small fluctuation in interest rates can drastically alter your monthly payment and total loan cost. For example, on a $300,000 loan, the difference between a 6% and a 7% interest rate can increase your monthly payment by nearly $200 and cost you tens of thousands of dollars in additional interest over the life of the loan. Using a calculator helps you stress-test your budget against potential rate changes.
The Impact of the Loan Term
Choosing between a 15-year and a 30-year fixed mortgage is a trade-off between monthly cash flow and total interest savings. A 15-year term will have significantly higher monthly payments because you are paying off the principal faster, but the interest rate is often lower, and the total interest paid over the life of the loan is drastically reduced compared to a 30-year term.
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 = parseInt(document.getElementById('loanTerm').value);
var propertyTax = parseFloat(document.getElementById('propertyTax').value);
var homeInsurance = parseFloat(document.getElementById('homeInsurance').value);
// Validation Check
var errorDiv = document.getElementById('errorMsg');
var resultsDiv = document.getElementById('resultsSection');
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm) || isNaN(propertyTax) || isNaN(homeInsurance)) {
errorDiv.style.display = 'block';
resultsDiv.style.display = 'none';
return;
}
if (homePrice <= 0 || interestRate < 0 || loanTerm <= 0) {
errorDiv.style.display = 'block';
errorDiv.innerHTML = "Please enter positive values.";
resultsDiv.style.display = 'none';
return;
}
errorDiv.style.display = 'none';
// Calculation Logic
var loanAmount = homePrice – downPayment;
// Handle case where down payment is greater than home price
if (loanAmount 0) {
var x = Math.pow(1 + monthlyRate, numberOfPayments);
monthlyPrincipalInterest = loanAmount * ((monthlyRate * x) / (x – 1));
} else {
// If interest rate is 0
monthlyPrincipalInterest = loanAmount / numberOfPayments;
}
var monthlyTax = propertyTax / 12;
var monthlyInsurance = homeInsurance / 12;
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance;
// Update UI
document.getElementById('resLoanAmount').innerText = '$' + loanAmount.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resPI').innerText = '$' + monthlyPrincipalInterest.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resTax').innerText = '$' + monthlyTax.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resIns').innerText = '$' + monthlyInsurance.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resTotal').innerText = '$' + totalMonthlyPayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
// Show Results
resultsDiv.style.display = 'block';
}