Please enter valid positive numbers for Home Price and Interest Rate.
Monthly Breakdown
Principal & Interest:$0.00
Property Tax:$0.00
Home Insurance:$0.00
HOA Fees:$0.00
Total Monthly Payment:$0.00
Loan Amount: $0
How to Calculate Your Mortgage Payment
Purchasing a home is one of the most significant financial decisions you will make in your lifetime. Understanding exactly how much you will pay each month is crucial for maintaining financial health. This Mortgage Payment Calculator helps you estimate your monthly housing costs by factoring in principal, interest, taxes, insurance, and HOA fees.
Understanding the PITI Formula
Most mortgage payments are made up of four specific components, commonly referred to by the acronym PITI:
Principal: The portion of your payment that goes toward paying down the original amount you borrowed. In the early years of a loan, this amount is small, but it grows over time.
Interest: The cost of borrowing money paid to the lender. On a standard amortization schedule, you pay more interest at the beginning of the loan term.
Taxes: Property taxes assessed by your local government. These are typically estimated annually and divided into 12 monthly payments held in escrow.
Insurance: Homeowners insurance protects your property against damage. Like taxes, this is often paid annually but collected monthly by your lender.
How Interest Rates Impact Your Buying Power
Even a small fluctuation in interest rates can drastically change your monthly payment and the total cost of your loan. For example, on a $400,000 loan, the difference between a 6% and a 7% interest rate can add hundreds of dollars to your monthly payment and tens of thousands of dollars in interest over the life of a 30-year loan.
The Role of the Down Payment
Your down payment directly reduces the principal loan amount. A larger down payment ($) lowers your monthly Principal & Interest (P&I) payment. Additionally, if you put down less than 20%, you may be required to pay Private Mortgage Insurance (PMI), which would further increase your monthly costs. Note that this calculator focuses on PITI and HOA, so be sure to factor in PMI if your down payment is low.
How to Use This Calculator
Home Price: Enter the purchase price of the property.
Down Payment: Input the cash amount you plan to pay upfront.
Loan Term: Select the duration of the mortgage (typically 15 or 30 years).
Interest Rate: Enter the current annual interest rate offered by your lender.
Taxes & Insurance: Input the estimated annual property tax and homeowners insurance costs to get an accurate total monthly figure.
By accurately inputting these figures, you can determine a budget that fits your financial lifestyle before you start house hunting.
function calculateMortgage() {
// 1. Get Elements
var homePriceInput = document.getElementById('homePrice');
var downPaymentInput = document.getElementById('downPayment');
var loanTermInput = document.getElementById('loanTerm');
var interestRateInput = document.getElementById('interestRate');
var propertyTaxInput = document.getElementById('propertyTax');
var insuranceInput = document.getElementById('insurance');
var hoaFeesInput = document.getElementById('hoaFees');
var errorDiv = document.getElementById('errorDisplay');
var resultDiv = document.getElementById('resultsSection');
// 2. Parse Values
var homePrice = parseFloat(homePriceInput.value);
var downPayment = parseFloat(downPaymentInput.value);
var loanTermYears = parseFloat(loanTermInput.value);
var annualRate = parseFloat(interestRateInput.value);
var annualTax = parseFloat(propertyTaxInput.value);
var annualIns = parseFloat(insuranceInput.value);
var monthlyHOA = parseFloat(hoaFeesInput.value);
// 3. Validation
if (isNaN(homePrice) || isNaN(annualRate) || homePrice <= 0 || annualRate < 0) {
errorDiv.style.display = "block";
resultDiv.style.display = "none";
return;
}
// Handle optional fields as 0 if empty
if (isNaN(downPayment)) downPayment = 0;
if (isNaN(annualTax)) annualTax = 0;
if (isNaN(annualIns)) annualIns = 0;
if (isNaN(monthlyHOA)) monthlyHOA = 0;
errorDiv.style.display = "none";
// 4. Calculation Logic
var loanAmount = homePrice – downPayment;
// Prevent negative loan amount
if (loanAmount < 0) loanAmount = 0;
var monthlyInterestRate = (annualRate / 100) / 12;
var numberOfPayments = loanTermYears * 12;
var monthlyPI = 0;
// Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
if (annualRate === 0) {
monthlyPI = loanAmount / numberOfPayments;
} else {
var mathPow = Math.pow(1 + monthlyInterestRate, numberOfPayments);
if (mathPow === 1) {
// Edge case handling for extremely small rates or errors
monthlyPI = loanAmount / numberOfPayments;
} else {
monthlyPI = loanAmount * (monthlyInterestRate * mathPow) / (mathPow – 1);
}
}
var monthlyTax = annualTax / 12;
var monthlyIns = annualIns / 12;
var totalMonthlyPayment = monthlyPI + monthlyTax + monthlyIns + monthlyHOA;
// 5. Update UI
document.getElementById('resPI').innerText = "$" + monthlyPI.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resTax').innerText = "$" + monthlyTax.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resIns').innerText = "$" + monthlyIns.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resHOA').innerText = "$" + monthlyHOA.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resTotal').innerText = "$" + totalMonthlyPayment.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resLoanAmount').innerText = "$" + loanAmount.toLocaleString('en-US', {maximumFractionDigits: 0});
resultDiv.style.display = "block";
}