Loan Summary:
Loan Amount:
Total Interest Paid (Over Life of Loan):
Total Cost of Loan:
Understanding Your Mortgage Calculation
Using a reliable mortgage calculator is the first step in the home-buying journey. It helps you understand exactly how much house you can afford by breaking down the monthly costs associated with owning a property.
What is Included in Your Monthly Payment?
Most homebuyers focus solely on the principal and interest, but your actual monthly obligation typically includes four key components, often referred to as PITI:
Principal: The portion of your payment that reduces the loan balance.
Interest: The cost of borrowing money from your lender.
Taxes: Property taxes charged by your local government, usually held in escrow.
Insurance: Homeowners insurance to protect against damage and liability.
How Interest Rates Affect Your Buying Power
Even a small change in interest rates can significantly impact your monthly payment. For example, on a $300,000 loan, a 1% increase in interest rate can raise your monthly payment by hundreds of dollars, increasing the total cost of the loan by tens of thousands over 30 years.
Why Include HOA Fees?
If you are buying a condo or a home in a planned community, Homeowners Association (HOA) fees are a mandatory monthly cost. While these fees don't pay down your loan, they affect your Debt-to-Income (DTI) ratio and your ability to qualify for a mortgage.
Frequently Asked Questions
What is a good down payment?
While 20% is the standard to avoid Private Mortgage Insurance (PMI), many lenders offer conventional loans with as little as 3-5% down. FHA loans require 3.5% down. Keep in mind that a lower down payment results in a higher monthly payment and more interest paid over time.
Does this calculator include PMI?
This calculator estimates Principal, Interest, Taxes, Insurance, and HOA. If your down payment is less than 20%, you may also owe Private Mortgage Insurance (PMI), which typically costs between 0.5% to 1% of the loan amount annually.
function calculateMortgage() {
// 1. Get Input Values using var
var homePrice = parseFloat(document.getElementById('homePrice').value);
var downPayment = parseFloat(document.getElementById('downPayment').value);
var loanTermYears = parseFloat(document.getElementById('loanTerm').value);
var annualRate = parseFloat(document.getElementById('interestRate').value);
var yearlyTax = parseFloat(document.getElementById('propertyTax').value);
var yearlyInsurance = parseFloat(document.getElementById('homeInsurance').value);
var monthlyHOA = parseFloat(document.getElementById('hoaFees').value);
// 2. Validate Inputs
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(loanTermYears) || isNaN(annualRate)) {
alert("Please enter valid numbers for Price, Down Payment, Term, and Rate.");
return;
}
// 3. Perform Calculations
var loanAmount = homePrice – downPayment;
// Handle case where down payment >= home price
if (loanAmount <= 0) {
alert("Down payment cannot be equal to or greater than the Home Price for a mortgage calculation.");
return;
}
var monthlyRate = (annualRate / 100) / 12;
var numberOfPayments = loanTermYears * 12;
// Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
var monthlyPI = 0;
if (annualRate === 0) {
monthlyPI = loanAmount / numberOfPayments;
} else {
monthlyPI = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
}
var monthlyTax = yearlyTax / 12;
var monthlyInsurance = yearlyInsurance / 12;
// Handle NaN for optional fields if they are empty
if (isNaN(monthlyTax)) monthlyTax = 0;
if (isNaN(monthlyInsurance)) monthlyInsurance = 0;
if (isNaN(monthlyHOA)) monthlyHOA = 0;
var totalMonthlyPayment = monthlyPI + monthlyTax + monthlyInsurance + monthlyHOA;
var totalCostOfLoan = (monthlyPI * numberOfPayments) + downPayment; // Principal + Interest + Downpayment (Purchase cost context)
// Alternatively, Total Cost of Loan usually refers to Total Payments (P+I)
var totalPayments = monthlyPI * numberOfPayments;
var totalInterest = totalPayments – loanAmount;
// 4. Update UI
// Helper function for currency formatting
function formatMoney(num) {
return "$" + num.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}
document.getElementById('res-pi').innerHTML = formatMoney(monthlyPI);
document.getElementById('res-tax').innerHTML = formatMoney(monthlyTax);
document.getElementById('res-ins').innerHTML = formatMoney(monthlyInsurance);
document.getElementById('res-hoa').innerHTML = formatMoney(monthlyHOA);
document.getElementById('res-total').innerHTML = formatMoney(totalMonthlyPayment);
document.getElementById('res-loan-amount').innerHTML = formatMoney(loanAmount);
document.getElementById('res-total-interest').innerHTML = formatMoney(totalInterest);
document.getElementById('res-total-cost').innerHTML = formatMoney(totalPayments);
// Show results container
document.getElementById('results').style.display = 'block';
}