Estimate your monthly payments and total interest costs.
30 Years
20 Years
15 Years
10 Years
Please enter valid numeric values for all fields.
Payment Breakdown
Principal & Interest:$0.00
Monthly Tax:$0.00
Monthly Insurance:$0.00
Total Monthly Payment:$0.00
Loan Summary:
Total Principal:$0.00
Total Interest Paid:$0.00
Total Cost of Loan:$0.00
function calculateMortgage() {
// Get Inputs
var homePrice = parseFloat(document.getElementById('mpHomePrice').value);
var downPayment = parseFloat(document.getElementById('mpDownPayment').value);
var interestRate = parseFloat(document.getElementById('mpInterestRate').value);
var loanTerm = parseInt(document.getElementById('mpLoanTerm').value);
var annualTax = parseFloat(document.getElementById('mpPropertyTax').value) || 0;
var annualInsurance = parseFloat(document.getElementById('mpInsurance').value) || 0;
var errorDiv = document.getElementById('mpErrorMessage');
var resultBox = document.getElementById('mpResultBox');
// Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm) || homePrice = home price
if (principal 0 && interestRate > 0) {
monthlyPrincipalInterest = principal * (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
} else if (principal > 0 && interestRate === 0) {
monthlyPrincipalInterest = principal / numberOfPayments;
}
var monthlyTax = annualTax / 12;
var monthlyInsurance = annualInsurance / 12;
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance;
var totalInterest = (monthlyPrincipalInterest * numberOfPayments) – principal;
if (totalInterest < 0) totalInterest = 0; // specific handle for 0 interest
var totalCost = principal + totalInterest;
// Formatting Currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
// Update DOM
document.getElementById('resPrincipalInterest').innerHTML = formatter.format(monthlyPrincipalInterest);
document.getElementById('resTax').innerHTML = formatter.format(monthlyTax);
document.getElementById('resInsurance').innerHTML = formatter.format(monthlyInsurance);
document.getElementById('resTotalMonthly').innerHTML = formatter.format(totalMonthlyPayment);
document.getElementById('resTotalPrincipal').innerHTML = formatter.format(principal);
document.getElementById('resTotalInterest').innerHTML = formatter.format(totalInterest);
document.getElementById('resTotalCost').innerHTML = formatter.format(totalCost);
resultBox.style.display = 'block';
}
Understanding Your Mortgage Calculation
Calculating your monthly mortgage payment is a critical step in the home-buying process. This tool helps you determine exactly how much a new home will cost you on a monthly basis, accounting for principal, interest, taxes, and insurance (often referred to as PITI).
How is the Monthly Payment Calculated?
The core of a mortgage payment is determined by the amortization formula. This formula calculates the fixed monthly payment required to pay off the loan balance in full by the end of the term.
Principal: The amount of money you borrow (Home Price minus Down Payment).
Interest: The cost of borrowing the money, expressed as a percentage rate.
Taxes & Insurance: Annual property taxes and homeowners insurance premiums are typically divided by 12 and added to your monthly mortgage bill to be held in escrow.
Why Your Interest Rate Matters
Even a small difference in interest rates can have a massive impact on your total loan cost. For example, on a $300,000 loan, a 1% difference in interest rate can change your monthly payment by nearly $200 and save (or cost) you over $60,000 in interest over the life of a 30-year loan.
15-Year vs. 30-Year Mortgages
Choosing the right loan term is a balancing act between monthly affordability and long-term savings:
30-Year Term: Offers lower monthly payments, making expensive homes more affordable month-to-month, but you will pay significantly more in total interest.
15-Year Term: Requires higher monthly payments, but usually comes with a lower interest rate and builds equity much faster.
Tips for Lowering Your Payment
If the calculated payment is higher than your budget allows, consider increasing your down payment to reduce the principal amount. Alternatively, improving your credit score before applying can help you secure a lower interest rate. Finally, shopping around for cheaper homeowners insurance can shave dollars off your monthly PITI.