Estimate your monthly payments, interest costs, and payoff date.
30 Years
20 Years
15 Years
10 Years
Total Monthly Payment:$0.00
Principal & Interest:$0.00
Taxes, Insurance & HOA:$0.00
Total Interest Paid:$0.00
Total Cost of Loan:$0.00
Est. Payoff Date:–
How to Calculate Your Mortgage Payment
Understanding your mortgage payment is crucial when budgeting for a new home. This calculator breaks down the costs associated with borrowing money for real estate, helping you determine exactly how much house you can afford. While the "sticker price" of a home is important, the monthly obligation is often the deciding factor for lenders and buyers alike.
Components of a Mortgage Payment (PITI)
Mortgage payments are typically made up of four main components, often referred to by the acronym PITI:
Principal: The portion of your payment that goes toward reducing the outstanding balance of your loan. In the early years of a mortgage, this amount is small, but it grows over time as you pay down interest.
Interest: The cost of borrowing money from your lender. This is calculated based on your annual percentage rate (APR) and remaining loan balance.
Taxes: Property taxes assessed by your local government. Lenders often collect this monthly and hold it in an escrow account to pay the tax bill when it's due.
Insurance: Homeowners insurance protects the property against damage. Like taxes, this is usually collected monthly into an escrow account.
Understanding Amortization
Amortization refers to the process of spreading out a loan into a series of fixed payments over time. Even though your total monthly payment for principal and interest remains constant (with a fixed-rate mortgage), the ratio changes. At the beginning of a 30-year term, the majority of your payment goes toward interest. As the loan matures, a larger portion is applied to the principal.
How Interest Rates Affect Your Buying Power
Even a small difference in interest rates can have a massive impact on your monthly payment and the total cost of the loan. For example, on a $300,000 loan, the difference between a 6% and a 7% interest rate can amount to nearly $200 extra per month and over $70,000 in additional interest paid over 30 years.
Tips for Lowering Your Monthly Payment
If the calculated payment is higher than your budget allows, consider these strategies:
Increase your down payment: Putting more than 20% down avoids Private Mortgage Insurance (PMI) and lowers the loan principal.
Improve your credit score: A higher credit score often qualifies you for lower interest rates.
Shop for lower insurance: Homeowners insurance premiums vary significantly between providers.
Consider a longer term: While a 15-year mortgage saves on total interest, a 30-year mortgage offers lower monthly payments.
// Set default date to today
var today = new Date();
var day = ("0" + today.getDate()).slice(-2);
var month = ("0" + (today.getMonth() + 1)).slice(-2);
var dateString = today.getFullYear() + "-" + (month) + "-" + (day);
document.getElementById("startDate").value = dateString;
function calculateMortgage() {
// 1. Get Inputs
var homePrice = parseFloat(document.getElementById("homePrice").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTermYears = parseInt(document.getElementById("loanTerm").value);
var propertyTaxYearly = parseFloat(document.getElementById("propertyTax").value);
var homeInsuranceYearly = parseFloat(document.getElementById("homeInsurance").value);
var hoaFeesMonthly = parseFloat(document.getElementById("hoaFees").value);
var startDateVal = document.getElementById("startDate").value;
// 2. Validate Inputs
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTermYears)) {
alert("Please enter valid numbers for Home Price, Down Payment, Interest Rate, and Term.");
return;
}
// Handle optional fields as 0 if empty
if (isNaN(propertyTaxYearly)) propertyTaxYearly = 0;
if (isNaN(homeInsuranceYearly)) homeInsuranceYearly = 0;
if (isNaN(hoaFeesMonthly)) hoaFeesMonthly = 0;
// 3. Core Calculations
var principal = homePrice – downPayment;
if (principal <= 0) {
alert("Down payment cannot be greater than or equal to Home Price.");
return;
}
// Monthly Interest Rate
var monthlyRate = (interestRate / 100) / 12;
// Total Number of Payments
var numberOfPayments = loanTermYears * 12;
// Calculate Monthly Principal & Interest (PI)
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPI = 0;
if (interestRate === 0) {
monthlyPI = principal / numberOfPayments;
} else {
monthlyPI = principal * ( (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1) );
}
// Calculate Escrow (Taxes + Insurance) + HOA
var monthlyTax = propertyTaxYearly / 12;
var monthlyInsurance = homeInsuranceYearly / 12;
var monthlyEscrowAndFees = monthlyTax + monthlyInsurance + hoaFeesMonthly;
// Total Monthly Payment
var totalMonthlyPayment = monthlyPI + monthlyEscrowAndFees;
// Total Cost Calculations
var totalPrincipalInterestCost = monthlyPI * numberOfPayments;
var totalInterestPaid = totalPrincipalInterestCost – principal;
var totalLoanCost = totalPrincipalInterestCost + (monthlyEscrowAndFees * numberOfPayments);
// Payoff Date Calculation
var start = new Date(startDateVal);
start.setMonth(start.getMonth() + numberOfPayments);
var payoffDateString = start.toLocaleDateString('en-US', { month: 'long', year: 'numeric' });
// 4. Update UI
// Helper for currency formatting
var fmt = new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' });
document.getElementById("displayTotalMonthly").innerText = fmt.format(totalMonthlyPayment);
document.getElementById("displayPrincipalInterest").innerText = fmt.format(monthlyPI);
document.getElementById("displayEscrow").innerText = fmt.format(monthlyEscrowAndFees);
document.getElementById("displayTotalInterest").innerText = fmt.format(totalInterestPaid);
document.getElementById("displayTotalCost").innerText = fmt.format(totalLoanCost);
document.getElementById("displayPayoffDate").innerText = payoffDateString;
// Show results
document.getElementById("results").style.display = "block";
// Scroll to results on mobile
if(window.innerWidth < 600) {
document.getElementById("results").scrollIntoView({behavior: "smooth"});
}
}