Estimate your monthly payments, including taxes and insurance.
30 Years
20 Years
15 Years
10 Years
Principal & Interest:$0.00
Monthly Property Tax:$0.00
Monthly Insurance:$0.00
Monthly HOA:$0.00
Total Monthly Payment:$0.00
function calculateMortgage() {
// Get Input Values
var homePrice = parseFloat(document.getElementById('homePrice').value);
var downPayment = parseFloat(document.getElementById('downPayment').value);
var annualRate = parseFloat(document.getElementById('interestRate').value);
var years = parseInt(document.getElementById('loanTerm').value);
var annualTax = parseFloat(document.getElementById('propertyTax').value);
var annualIns = parseFloat(document.getElementById('homeInsurance').value);
var monthlyHOA = parseFloat(document.getElementById('hoaFees').value);
// Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(annualRate) || isNaN(years)) {
alert("Please enter valid numbers for Home Price, Down Payment, Interest Rate, and Term.");
return;
}
// Handle optional fields empty strings as 0
if (isNaN(annualTax)) annualTax = 0;
if (isNaN(annualIns)) annualIns = 0;
if (isNaN(monthlyHOA)) monthlyHOA = 0;
// Derived Values
var principal = homePrice – downPayment;
var monthlyRate = (annualRate / 100) / 12;
var numberOfPayments = years * 12;
var monthlyPI = 0;
// Logic: Amortization Formula M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
if (annualRate === 0) {
monthlyPI = principal / numberOfPayments;
} else {
var compoundFactor = Math.pow(1 + monthlyRate, numberOfPayments);
monthlyPI = principal * (monthlyRate * compoundFactor) / (compoundFactor – 1);
}
// Monthly Components
var monthlyTax = annualTax / 12;
var monthlyIns = annualIns / 12;
var totalMonthly = monthlyPI + monthlyTax + monthlyIns + monthlyHOA;
// Check valid result
if (principal < 0) {
alert("Down payment cannot be larger than the home price.");
return;
}
// Display Results
document.getElementById('resPI').innerHTML = "$" + monthlyPI.toFixed(2).replace(/\B(?=(\d{3})+(?!\d))/g, ",");
document.getElementById('resTax').innerHTML = "$" + monthlyTax.toFixed(2).replace(/\B(?=(\d{3})+(?!\d))/g, ",");
document.getElementById('resIns').innerHTML = "$" + monthlyIns.toFixed(2).replace(/\B(?=(\d{3})+(?!\d))/g, ",");
document.getElementById('resHOA').innerHTML = "$" + monthlyHOA.toFixed(2).replace(/\B(?=(\d{3})+(?!\d))/g, ",");
document.getElementById('resTotal').innerHTML = "$" + totalMonthly.toFixed(2).replace(/\B(?=(\d{3})+(?!\d))/g, ",");
document.getElementById('resultBox').style.display = 'block';
}
Understanding Your Mortgage Calculation
Whether you are a first-time homebuyer or looking to refinance, understanding exactly where your monthly payment goes is crucial for financial planning. This Mortgage Payment Calculator breaks down the four distinct costs that make up your PITI (Principal, Interest, Taxes, and Insurance).
The PITI Formula
Most mortgage payments are composed of four parts, often abbreviated as PITI:
Principal: The portion of your payment that reduces the loan balance. In the early years of a 30-year mortgage, this amount is small, but it grows over time as you pay down the debt.
Interest: The fee charged by the lender for borrowing the money. Because mortgages are amortized, you pay significantly more interest in the beginning of the loan term.
Taxes: Real estate property taxes are assessed by your local government. Lenders often collect this monthly and hold it in an escrow account to pay the bill annually on your behalf.
Insurance: Homeowners insurance protects the property against damage. Like taxes, this is usually broken down into monthly payments and paid via escrow.
How Interest Rates Affect Affordability
Even a small change in interest rates can have a massive impact on your monthly obligation. For example, on a $300,000 loan, the difference between a 6% and a 7% interest rate is roughly $200 per month. Over the life of a 30-year loan, that single percentage point can cost you over $70,000 in additional interest payments.
Using This Calculator for Budgeting
When using this calculator, ensure you don't just look at the Principal and Interest. Don't forget to include Homeowners Association (HOA) fees if you are buying a condo or a home in a planned community, as these are paid separately from your mortgage but directly affect your monthly housing budget. A debt-to-income (DTI) ratio of 36% or lower is generally recommended by financial experts to ensure you aren't "house poor."
Frequently Asked Questions
What is an amortization schedule?
An amortization schedule is a table detailing each periodic payment on an amortizing loan. It shows the amount of principal and the amount of interest that comprise each payment until the loan is paid off at the end of its term.
Should I choose a 15-year or 30-year term?
A 15-year mortgage usually offers a lower interest rate and significantly lower total interest costs over the life of the loan. However, the monthly payments are much higher than a 30-year mortgage, which offers flexibility but costs more in the long run.