Calculate your estimated monthly mortgage payment, including principal, interest, taxes, and insurance (PITI).
Typically 20% to avoid PMI
30 Years
20 Years
15 Years
10 Years
Approx. 1-1.5% of home value
Estimated Monthly Payment$0.00
Principal & Interest:$0.00
Property Tax (Monthly):$0.00
Home Insurance (Monthly):$0.00
Loan Amount:$0.00
Total Interest Paid (Over Term):$0.00
Understanding Your Mortgage Calculation
Purchasing a home is likely the largest financial commitment you will make in your lifetime. Understanding how your monthly payments are calculated is crucial for maintaining financial health. This calculator breaks down the PITI (Principal, Interest, Taxes, and Insurance) to give you a realistic view of affordability.
Components of a Mortgage Payment
Most lenders look at four distinct parts when calculating your monthly obligation:
Principal: The portion of your payment that goes directly toward paying down the loan balance.
Interest: The cost of borrowing money from the lender. In the early years of a standard amortization schedule, the majority of your payment goes toward interest.
Taxes: Property taxes assessed by your local government. Lenders often collect this monthly and hold it in an escrow account to pay the bill when it's due.
Insurance: Homeowners insurance protects the property against damage. Like taxes, this is often paid via escrow.
How Interest Rates Impact Your Loan
Even a small fluctuation in interest rates can significantly affect your monthly payment and the total cost 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 interest paid by tens of thousands over a 30-year term.
The 28/36 Rule of Affordability
When determining if you can afford a mortgage, financial experts often cite the 28/36 rule:
Your housing expenses (PITI) should not exceed 28% of your gross monthly income.
Your total debt service (housing + credit cards + car loans + student loans) should not exceed 36% of your gross monthly income.
Use the results from the calculator above to ensure your estimated payment fits within these guidelines for a comfortable financial future.
function calculateMortgage() {
// 1. Get Input Values
var homePrice = parseFloat(document.getElementById("homePrice").value) || 0;
var downPayment = parseFloat(document.getElementById("downPayment").value) || 0;
var interestRate = parseFloat(document.getElementById("interestRate").value) || 0;
var loanTermYears = parseInt(document.getElementById("loanTerm").value) || 30;
var annualTax = parseFloat(document.getElementById("propertyTax").value) || 0;
var annualInsurance = parseFloat(document.getElementById("homeInsurance").value) || 0;
// 2. Validate Key Inputs
if (homePrice <= 0) {
alert("Please enter a valid Home Price.");
return;
}
// 3. Perform Calculations
var loanAmount = homePrice – downPayment;
// Handle negative loan amount
if (loanAmount < 0) {
loanAmount = 0;
}
var monthlyTax = annualTax / 12;
var monthlyInsurance = annualInsurance / 12;
var monthlyInterestRate = (interestRate / 100) / 12;
var numberOfPayments = loanTermYears * 12;
var monthlyPI = 0;
// Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
if (interestRate === 0) {
monthlyPI = loanAmount / numberOfPayments;
} else {
var mathPower = Math.pow(1 + monthlyInterestRate, numberOfPayments);
monthlyPI = loanAmount * (monthlyInterestRate * mathPower) / (mathPower – 1);
}
// Handle NaN cases (e.g. if term is 0)
if (!isFinite(monthlyPI)) {
monthlyPI = 0;
}
var totalMonthlyPayment = monthlyPI + monthlyTax + monthlyInsurance;
var totalPaymentOverLife = monthlyPI * numberOfPayments;
var totalInterest = totalPaymentOverLife – loanAmount;
// 4. Format and Display Results
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById("totalMonthlyPayment").innerHTML = formatter.format(totalMonthlyPayment);
document.getElementById("piPayment").innerHTML = formatter.format(monthlyPI);
document.getElementById("taxMonthly").innerHTML = formatter.format(monthlyTax);
document.getElementById("insMonthly").innerHTML = formatter.format(monthlyInsurance);
document.getElementById("loanAmountResult").innerHTML = formatter.format(loanAmount);
document.getElementById("totalInterestResult").innerHTML = formatter.format(totalInterest);
// Show the result section
document.getElementById("resultsArea").style.display = "block";
}