Please enter valid positive numbers for all fields.
Estimated Monthly Payment
$0.00
Principal & Interest:$0.00
Property Tax (Monthly):$0.00
Home Insurance (Monthly):$0.00
HOA Fees:$0.00
Total Loan Amount:$0.00
Total Interest Paid:$0.00
function calculateMortgage() {
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);
var errorMsg = document.getElementById('errorMsg');
var resultSection = document.getElementById('resultSection');
// Reset error
errorMsg.style.display = 'none';
// Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(loanTerm) || isNaN(interestRate) ||
isNaN(propertyTax) || isNaN(homeInsurance) || isNaN(hoaFees) ||
homePrice < 0 || downPayment < 0 || loanTerm <= 0 || interestRate < 0) {
errorMsg.style.display = 'block';
resultSection.style.display = 'none';
return;
}
// Core Logic
var principal = homePrice – downPayment;
// Handle edge case: principal is 0 or negative
if (principal <= 0) {
document.getElementById('totalMonthlyPayment').innerText = '$0.00';
document.getElementById('piAmount').innerText = '$0.00';
// Show result even if paid off, but values are zero
resultSection.style.display = 'block';
return;
}
var monthlyInterestRate = (interestRate / 100) / 12;
var numberOfPayments = loanTerm * 12;
var monthlyPrincipalAndInterest = 0;
if (interestRate === 0) {
monthlyPrincipalAndInterest = principal / numberOfPayments;
} else {
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var x = Math.pow(1 + monthlyInterestRate, numberOfPayments);
monthlyPrincipalAndInterest = principal * ((monthlyInterestRate * x) / (x – 1));
}
var monthlyTax = propertyTax / 12;
var monthlyInsurance = homeInsurance / 12;
var totalMonthlyPayment = monthlyPrincipalAndInterest + monthlyTax + monthlyInsurance + hoaFees;
var totalRepayment = monthlyPrincipalAndInterest * numberOfPayments;
var totalInterest = totalRepayment – principal;
// Formatting Output
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById('totalMonthlyPayment').innerText = formatter.format(totalMonthlyPayment);
document.getElementById('piAmount').innerText = formatter.format(monthlyPrincipalAndInterest);
document.getElementById('taxAmount').innerText = formatter.format(monthlyTax);
document.getElementById('insAmount').innerText = formatter.format(monthlyInsurance);
document.getElementById('hoaAmount').innerText = formatter.format(hoaFees);
document.getElementById('loanAmountResult').innerText = formatter.format(principal);
document.getElementById('totalInterestResult').innerText = formatter.format(totalInterest);
resultSection.style.display = 'block';
}
Understanding Your Mortgage Payment
Purchasing a home is likely the largest financial commitment you will make in your lifetime. Understanding how your monthly mortgage payment is calculated is essential for budgeting and determining exactly how much house you can afford. This Mortgage Calculator breaks down the costs associated with homeownership, moving beyond just the sticker price of the home to reveal the true monthly cost.
The 4 Components of a Mortgage Payment (PITI)
Most lenders use the acronym PITI to describe the sum of a monthly mortgage payment:
Principal: The portion of your payment that goes directly toward reducing the outstanding loan balance. In the early years of a loan, this amount is small, but it grows over time.
Interest: The fee charged by the lender for borrowing the money. Interest payments are front-loaded, meaning you pay more interest at the start of your loan term.
Taxes: Property taxes assessed by your local government. These are often collected by the lender in an escrow account and paid annually on your behalf.
Insurance: Homeowners insurance protects your property against damage. Like taxes, this is usually bundled into your monthly payment via escrow.
How Interest Rates Affect Affordability
Even a small change in interest rates can drastically alter your monthly payment and the total cost of the loan. For example, on a $300,000 loan over 30 years:
At 4.0%, the monthly P&I payment is approximately $1,432.
At 6.0%, the monthly P&I payment jumps to approximately $1,799.
That difference of $367 per month adds up to over $132,000 in extra interest paid over the life of the loan. Use the calculator above to scenario-test different rates to see how they impact your budget.
Loan Term: 15-Year vs. 30-Year
The length of your loan affects both your monthly payment and total interest paid. A 30-year fixed-rate mortgage offers lower monthly payments, making the home more affordable on a month-to-month basis. However, you will pay significantly more interest over the life of the loan compared to a 15-year mortgage.
A 15-year loan will have higher monthly payments because you are paying off the principal faster, but the interest rate is often lower, and the total interest cost is drastically reduced. Buyers with strong cash flow often prefer shorter terms to build equity faster.
Don't Forget HOA Fees
If you are buying a condo, townhouse, or a home in a planned community, you likely have to pay Homeowners Association (HOA) fees. While these are usually paid directly to the association and not the lender, lenders factor them into your debt-to-income ratio. We've included an input for HOA fees in this calculator to ensure your "Total Monthly Payment" reflects the reality of your housing expenses.