Calculate your estimated monthly payment including principal, interest, taxes, and insurance (PITI).
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Please check your inputs. Home price must be greater than down payment, and interest rate must be valid.
Total Monthly Payment
Principal & Interest
Property Taxes (Monthly)
Home Insurance (Monthly)
HOA Fees
Total Loan Amount
function calculateMortgage() {
// 1. Get input values using standard DOM methods
var homePrice = parseFloat(document.getElementById('homePrice').value);
var downPayment = parseFloat(document.getElementById('downPayment').value);
var interestRate = parseFloat(document.getElementById('interestRate').value);
var loanTerm = parseFloat(document.getElementById('loanTerm').value);
var propertyTax = parseFloat(document.getElementById('propertyTax').value);
var homeInsurance = parseFloat(document.getElementById('homeInsurance').value);
var hoaFees = parseFloat(document.getElementById('hoaFees').value);
// 2. Defaulting optional fields to 0 if empty
if (isNaN(downPayment)) downPayment = 0;
if (isNaN(propertyTax)) propertyTax = 0;
if (isNaN(homeInsurance)) homeInsurance = 0;
if (isNaN(hoaFees)) hoaFees = 0;
// 3. Validation Logic
var errorDiv = document.getElementById('errorMessage');
var resultDiv = document.getElementById('resultsSection');
if (isNaN(homePrice) || isNaN(interestRate) || isNaN(loanTerm) || homePrice <= 0 || loanTerm = homePrice) {
errorDiv.style.display = 'block';
errorDiv.innerText = "Down payment cannot be equal to or greater than the home price.";
resultDiv.style.display = 'none';
return;
}
errorDiv.style.display = 'none';
// 4. Core Calculations
var principal = homePrice – downPayment;
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = loanTerm * 12;
// Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
var monthlyPI = 0;
if (interestRate === 0) {
monthlyPI = principal / numberOfPayments;
} else {
var x = Math.pow(1 + monthlyRate, numberOfPayments);
monthlyPI = (principal * x * monthlyRate) / (x – 1);
}
var monthlyTax = propertyTax / 12;
var monthlyIns = homeInsurance / 12;
var totalMonthlyPayment = monthlyPI + monthlyTax + monthlyIns + hoaFees;
// 5. Update UI
document.getElementById('totalMonthly').innerText = "$" + totalMonthlyPayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('piResult').innerText = "$" + monthlyPI.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('taxResult').innerText = "$" + monthlyTax.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('insResult').innerText = "$" + monthlyIns.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('hoaResult').innerText = "$" + hoaFees.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('loanAmountResult').innerText = "$" + principal.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 0});
// Show results
resultDiv.style.display = 'block';
}
Understanding Your Mortgage: Beyond the Monthly Payment
Buying a home is one of the most significant financial decisions you will make in your lifetime. While the listing price is the number that grabs headlines, the reality of affordability comes down to your monthly mortgage payment. Our Mortgage Payment Estimator is designed to give you a clear, granular view of what owning a specific property will actually cost you on a month-to-month basis.
The 4 Pillars of a Mortgage Payment (PITI)
When lenders calculate your eligibility, they look at "PITI." Understanding these four components is crucial for accurate budgeting:
Principal: The portion of your payment that goes toward paying down the actual loan balance. In the early years of a 30-year mortgage, this amount is quite small.
Interest: The cost of borrowing money. Initially, the vast majority of your payment goes here. As the loan matures, the interest portion decreases while the principal portion increases (amortization).
Taxes: Property taxes are usually collected by your lender into an escrow account and paid annually to your local government. These can vary significantly by county and school district.
Insurance: Homeowners insurance protects your property against damage. Like taxes, this is often bundled into your monthly payment via escrow.
How Interest Rates Impact Your Buying Power
Even a small fluctuation in interest rates can dramatically change your monthly obligation and total loan cost. For example, on a $300,000 loan, the difference between a 6% and a 7% interest rate isn't just 1%—it can translate to hundreds of dollars more per month and tens of thousands over the life of the loan. Use the calculator above to scenario-plan different rates to see how "rate sensitive" your budget is.
Don't Forget the "Hidden" Costs: HOAs
If you are buying a condo, townhouse, or a home in a planned community, you will likely encounter Homeowners Association (HOA) fees. Unlike taxes and insurance, HOA fees are rarely included in the mortgage loan itself, but they are a mandatory monthly expense that affects your debt-to-income ratio. Always input the HOA fees in the calculator to ensure you aren't exceeding your monthly housing budget.
Frequently Asked Questions
What is a good rule of thumb for affordability?
Many financial experts recommend the 28/36 rule: spend no more than 28% of your gross monthly income on housing expenses and no more than 36% on total debt (including cars, student loans, etc.).
How does the loan term affect my payment?
A 15-year mortgage will have higher monthly payments than a 30-year mortgage because you are paying the principal back faster. However, the total interest paid over the life of a 15-year loan is significantly lower.
What happens if I put less than 20% down?
If your down payment is under 20%, lenders typically require Private Mortgage Insurance (PMI). This is an extra monthly fee not included in the standard calculation above unless added to your insurance or tax estimate manually. It protects the lender in case of default.