Estimate your monthly payments, including taxes and insurance.
$
$
%
Yrs
$
$
Estimated Monthly Payment
$0.00
Principal & Interest:$0.00
Property Tax (Monthly):$0.00
Home Insurance (Monthly):$0.00
Total Loan Amount:$0.00
Total Interest Paid:$0.00
Payoff Date:–
Understanding Your Mortgage Calculation
Purchasing a home is likely the largest financial decision you will make in your lifetime. Using a comprehensive Mortgage Payment Calculator is essential to understanding not just the purchase price, but the actual monthly impact on your budget. This tool helps break down the principal, interest, taxes, and insurance (often referred to as PITI) so you can determine exactly what you can afford.
Key Factors That Influence Your Monthly Payment
While the sticker price of a home captures the headlines, four main components dictate your actual monthly outlay:
Principal: The portion of your payment that goes directly toward paying down the loan balance. In the early years of a mortgage, this amount is small compared to the interest.
Interest: The cost of borrowing money. Even a fractional difference in your interest rate (e.g., 6.5% vs 7.0%) can change your monthly payment by hundreds of dollars and your total loan cost by tens of thousands.
Property Taxes: Assessed by your local government, this fee is usually bundled into your monthly mortgage payment through an escrow account. High-tax areas can significantly reduce your buying power.
Homeowners Insurance: Lenders require insurance to protect the asset. Like taxes, this is typically paid monthly into escrow.
The Impact of the Loan Term
Most buyers opt for a standard 30-year fixed-rate mortgage because it offers the lowest monthly payment, spreading the repayment over three decades. However, a 15-year term usually comes with a lower interest rate. While the monthly payments on a 15-year loan are higher, the total interest paid over the life of the loan is drastically lower. Use the "Loan Term" field in the calculator above to compare these scenarios.
How Down Payments Affect Interest
Your down payment does more than just reduce the loan amount. A down payment of 20% or more typically allows you to avoid Private Mortgage Insurance (PMI), a monthly fee charged to borrowers with less equity. While this calculator focuses on PITI, remember that putting less than 20% down may add $100-$300 to your monthly bill in PMI costs until you reach 20% equity.
Calculating Your "True" Affordability
Financial experts often recommend the 28/36 rule. Your housing expenses (Principal, Interest, Taxes, Insurance) should not exceed 28% of your gross monthly income, and your total debt-to-income ratio (housing plus credit cards, student loans, car payments) should not exceed 36%. Before applying for a pre-approval, run the numbers here to ensure your comfortable budget aligns with current market rates and property tax estimates in your desired neighborhood.
function calculateMortgage() {
// 1. 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 = parseFloat(document.getElementById("loanTerm").value);
var propertyTaxAnnual = parseFloat(document.getElementById("propertyTax").value);
var homeInsuranceAnnual = parseFloat(document.getElementById("homeInsurance").value);
// 2. Validate Inputs
if (isNaN(homePrice) || homePrice <= 0) {
alert("Please enter a valid Home Price.");
return;
}
if (isNaN(downPayment) || downPayment < 0) {
downPayment = 0;
}
if (isNaN(interestRate) || interestRate < 0) {
alert("Please enter a valid Interest Rate.");
return;
}
if (isNaN(loanTerm) || loanTerm home price
if (loanAmount < 0) {
alert("Down payment cannot be greater than the home price.");
return;
}
var monthlyInterestRate = (interestRate / 100) / 12;
var numberOfPayments = loanTerm * 12;
// Amortization Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPrincipalInterest = 0;
if (interestRate === 0) {
monthlyPrincipalInterest = loanAmount / numberOfPayments;
} else {
monthlyPrincipalInterest = loanAmount * (
(monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) /
(Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1)
);
}
// Calculate Escrow components
var monthlyTax = propertyTaxAnnual / 12;
var monthlyInsurance = homeInsuranceAnnual / 12;
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance;
var totalInterestPaid = (monthlyPrincipalInterest * numberOfPayments) – loanAmount;
// Calculate Payoff Date
var today = new Date();
var payoffYear = today.getFullYear() + loanTerm;
var payoffMonth = today.toLocaleString('default', { month: 'short' });
var payoffDateString = payoffMonth + " " + payoffYear;
// 4. Formatting output (Currency)
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
// 5. Display Results
document.getElementById("monthlyPaymentResult").innerHTML = formatter.format(totalMonthlyPayment);
document.getElementById("piResult").innerHTML = formatter.format(monthlyPrincipalInterest);
document.getElementById("taxResult").innerHTML = formatter.format(monthlyTax);
document.getElementById("insuranceResult").innerHTML = formatter.format(monthlyInsurance);
document.getElementById("loanAmountResult").innerHTML = formatter.format(loanAmount);
document.getElementById("totalInterestResult").innerHTML = formatter.format(totalInterestPaid);
document.getElementById("payoffDateResult").innerHTML = payoffDateString;
// Show the results section
document.getElementById("resultsSection").style.display = "block";
// Smooth scroll to results
document.getElementById("resultsSection").scrollIntoView({ behavior: 'smooth' });
}