Please enter valid numeric values greater than zero.
Total Monthly Payment:$0.00
Principal & Interest:$0.00
Property Tax (Monthly):$0.00
Home Insurance (Monthly):$0.00
HOA Fees:$0.00
Loan Amount:$0.00
Total Interest Paid:$0.00
Understanding Your Mortgage Payment
Using a comprehensive mortgage calculator is the first step in determining how much home you can afford. While many simple calculators only show the principal and interest, a true estimate of your monthly obligation includes PITI: Principal, Interest, Taxes, and Insurance.
Components of a Mortgage Payment (PITI)
When you take out a home loan, your monthly bill is typically composed of four distinct parts:
Principal: The portion of your payment that goes toward paying down the loan balance (the amount you borrowed).
Interest: The cost of borrowing money, paid to the lender. In the early years of a mortgage, a larger percentage of your payment goes toward interest.
Taxes: Property taxes assessed by your local government. These are often collected by the lender in an escrow account and paid on your behalf annually.
Insurance: Homeowner's insurance protects your property against damage. Like taxes, premiums are often divided into monthly installments and held in escrow.
How Down Payment Affects Your Loan
The down payment is the upfront cash you pay toward the purchase of the home. A larger down payment reduces the principal loan amount, which lowers your monthly payments and total interest paid over the life of the loan. Typically, if you put down less than 20% of the home's value, you may also be required to pay Private Mortgage Insurance (PMI), which increases your monthly costs.
Interest Rates and Loan Terms
Your interest rate and the length of your loan (term) significantly impact your monthly payment. A 30-year fixed-rate mortgage offers lower monthly payments but results in more total interest paid compared to a 15-year term. Conversely, a lower interest rate can save you tens of thousands of dollars over the life of the loan. It is crucial to shop around with different lenders to secure the best rate possible.
Calculating Affordability
Financial experts generally recommend that your total monthly housing costs (PITI + HOA) should not exceed 28% of your gross monthly income. This is known as the "front-end ratio." Additionally, your total debt payments (including student loans, car payments, and credit cards) plus your housing costs should typically stay below 36% of your gross income (the "back-end ratio").
function calculateMortgage() {
// Retrieve Input Values
var homePrice = parseFloat(document.getElementById("homePrice").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var loanTermYears = parseFloat(document.getElementById("loanTerm").value);
var interestRateAnnual = parseFloat(document.getElementById("interestRate").value);
var propertyTaxAnnual = parseFloat(document.getElementById("propertyTax").value);
var homeInsuranceAnnual = parseFloat(document.getElementById("homeInsurance").value);
var hoaFeesMonthly = parseFloat(document.getElementById("hoaFees").value);
var errorMsg = document.getElementById("errorMsg");
var resultSection = document.getElementById("resultSection");
// Basic Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(loanTermYears) || isNaN(interestRateAnnual) ||
homePrice <= 0 || loanTermYears <= 0) {
errorMsg.style.display = "block";
resultSection.style.display = "none";
return;
}
// Logic & Calculations
errorMsg.style.display = "none";
var principal = homePrice – downPayment;
// Handle case where down payment is larger than home price
if (principal < 0) principal = 0;
var monthlyInterestRate = (interestRateAnnual / 100) / 12;
var numberOfPayments = loanTermYears * 12;
var monthlyPrincipalInterest = 0;
// Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
if (interestRateAnnual === 0) {
monthlyPrincipalInterest = principal / numberOfPayments;
} else {
monthlyPrincipalInterest = principal *
(monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) /
(Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
}
var monthlyTax = isNaN(propertyTaxAnnual) ? 0 : propertyTaxAnnual / 12;
var monthlyInsurance = isNaN(homeInsuranceAnnual) ? 0 : homeInsuranceAnnual / 12;
var monthlyHOA = isNaN(hoaFeesMonthly) ? 0 : hoaFeesMonthly;
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance + monthlyHOA;
var totalCostOfLoan = (monthlyPrincipalInterest * numberOfPayments);
var totalInterestPaid = totalCostOfLoan – principal;
// Formatting currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
});
// Updating the DOM
document.getElementById("totalMonthlyDisplay").innerHTML = formatter.format(totalMonthlyPayment);
document.getElementById("piDisplay").innerHTML = formatter.format(monthlyPrincipalInterest);
document.getElementById("taxDisplay").innerHTML = formatter.format(monthlyTax);
document.getElementById("insDisplay").innerHTML = formatter.format(monthlyInsurance);
document.getElementById("hoaDisplay").innerHTML = formatter.format(monthlyHOA);
document.getElementById("loanAmountDisplay").innerHTML = formatter.format(principal);
document.getElementById("totalInterestDisplay").innerHTML = formatter.format(totalInterestPaid);
// Show Results
resultSection.style.display = "block";
}