Calculating your potential monthly mortgage payment is a critical first step in the home buying process. This Comprehensive Mortgage Calculator helps you estimate not just the loan repayment, but the total cost of homeownership including taxes, insurance, and association fees.
Components of Your Monthly Payment
While the "headline" number on a mortgage is often the Principal and Interest, your actual monthly check to the bank will likely include several other buckets. This is often referred to as PITI (Principal, Interest, Taxes, and Insurance).
Principal: The portion of your payment that pays down the actual money you borrowed. In the early years of a loan, this amount is small.
Interest: The fee the lender charges for lending you money. At the start of a 30-year term, interest makes up the majority of your payment.
Escrow (Taxes & Insurance): Most lenders require you to pay 1/12th of your annual property taxes and homeowners insurance each month. They hold this in an escrow account and pay the bills on your behalf when they are due.
HOA Fees: If you buy a condo or a home in a planned community, you may have Homeowners Association fees. While these are usually paid directly to the association, our calculator includes them to give you a true picture of your monthly budget.
How Interest Rates Affect Your Buying Power
Even a small change in interest rates can significantly impact your monthly payment and the total interest paid over the life of the loan. For example, on a $300,000 loan, a difference of just 1% in the interest rate can change your monthly payment by hundreds of dollars and your total lifetime cost by tens of thousands.
Tips for Lowering Your Monthly Payment
Increase Your Down Payment: Putting more money down reduces the principal loan amount, which lowers your monthly obligation and may eliminate the need for Private Mortgage Insurance (PMI).
Improve Your Credit Score: A higher credit score often qualifies you for lower interest rates.
Shop Around: Different lenders offer different rates and closing costs. It pays to compare.
Consider a 15-Year Term: While your monthly payment will be higher, the total interest paid over the life of the loan is drastically lower compared to a 30-year term.
Why Use This Calculator?
Unlike simple calculators that only show Principal and Interest, this tool allows you to input "hidden" costs like HOA fees and taxes. This ensures you aren't blindsided by the actual cost of owning a home. Always ensure your total housing costs do not exceed a manageable percentage of your monthly income—financial advisors often recommend keeping this below 28%.
function calculateMortgage() {
// Get Input Values
var homePrice = parseFloat(document.getElementById('mc-home-price').value);
var downPayment = parseFloat(document.getElementById('mc-down-payment').value);
var interestRate = parseFloat(document.getElementById('mc-interest-rate').value);
var loanTermYears = parseFloat(document.getElementById('mc-loan-term').value);
var propertyTaxYear = parseFloat(document.getElementById('mc-property-tax').value);
var insuranceYear = parseFloat(document.getElementById('mc-insurance').value);
var hoaMonth = parseFloat(document.getElementById('mc-hoa').value);
// Validate Inputs
if (isNaN(homePrice) || homePrice < 0) homePrice = 0;
if (isNaN(downPayment) || downPayment < 0) downPayment = 0;
if (isNaN(interestRate) || interestRate < 0) interestRate = 0;
if (isNaN(propertyTaxYear) || propertyTaxYear < 0) propertyTaxYear = 0;
if (isNaN(insuranceYear) || insuranceYear < 0) insuranceYear = 0;
if (isNaN(hoaMonth) || hoaMonth < 0) hoaMonth = 0;
// Calculate Loan Amount
var loanAmount = homePrice – downPayment;
if (loanAmount < 0) loanAmount = 0;
// Monthly Interest Rate and Number of Payments
var monthlyRate = (interestRate / 100) / 12;
var numberOfPayments = loanTermYears * 12;
// Calculate Principal & Interest (P&I)
var monthlyPI = 0;
if (interestRate === 0) {
monthlyPI = loanAmount / numberOfPayments;
} else {
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
monthlyPI = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
}
if (isNaN(monthlyPI) || !isFinite(monthlyPI)) {
monthlyPI = 0;
}
// Calculate Monthly Taxes and Insurance
var monthlyTax = propertyTaxYear / 12;
var monthlyIns = insuranceYear / 12;
// Total Monthly Payment
var totalMonthly = monthlyPI + monthlyTax + monthlyIns + hoaMonth;
// Format Currency Function
function formatCurrency(num) {
return '$' + num.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}
// Update UI
document.getElementById('mc-result-pi').innerHTML = formatCurrency(monthlyPI);
document.getElementById('mc-result-tax').innerHTML = formatCurrency(monthlyTax);
document.getElementById('mc-result-ins').innerHTML = formatCurrency(monthlyIns);
document.getElementById('mc-result-hoa').innerHTML = formatCurrency(hoaMonth);
document.getElementById('mc-total-monthly').innerHTML = formatCurrency(totalMonthly);
document.getElementById('mc-loan-amount').innerHTML = formatCurrency(loanAmount);
// Show Results
document.getElementById('mc-results-area').style.display = 'block';
}