Estimate your monthly payments including PITI (Principal, Interest, Taxes, and Insurance)
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Years
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Total Monthly Payment
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Principal & Interest
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Taxes (Monthly)
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Insurance (Monthly)
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Total Interest Paid
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Understanding Your Mortgage Calculation
Buying a home is one of the largest financial decisions you will make. Using a comprehensive mortgage calculator is essential to understand exactly what your monthly obligations will be. While many buyers focus solely on the principal and interest, the "real" cost of homeownership includes several other factors commonly referred to as PITI.
What is PITI?
PITI stands for Principal, Interest, Taxes, and Insurance. These are the four main components that make up your monthly mortgage payment:
Principal: The portion of the payment that goes toward paying down the loan balance.
Interest: The cost of borrowing the money, paid to the lender.
Taxes: Property taxes assessed by your local government, typically collected by the lender in an escrow account.
Insurance: Homeowners insurance to protect the property, also usually held in escrow.
How Interest Rates Affect Your Payment
Even a small difference in interest rates can have a massive impact on your monthly payment and the total cost of the loan over time. For example, on a $300,000 loan, the difference between a 6% and a 7% interest rate can equate to hundreds of dollars a month and tens of thousands of dollars over the life of a 30-year loan. It is crucial to shop around for the best rates and improve your credit score before applying.
Private Mortgage Insurance (PMI) and HOA Fees
If your down payment is less than 20% of the home price, lenders generally require Private Mortgage Insurance (PMI) to protect them in case of default. Additionally, if you are buying a condo or a home in a planned community, you may be subject to Homeowners Association (HOA) fees. While HOA fees are usually paid directly to the association and not the lender, they are a critical part of your monthly housing budget and are included in our calculator to give you a realistic total.
Choosing the Right Loan Term
The most common loan terms are 15-year and 30-year fixed-rate mortgages. A 30-year term offers lower monthly payments but results in significantly higher total interest paid. A 15-year term has higher monthly payments but allows you to build equity much faster and save money on interest. Use the calculator above to compare how different terms affect your budget.
function calculateMortgage() {
// 1. Get input values
var price = parseFloat(document.getElementById('mc-price').value);
var downPayment = parseFloat(document.getElementById('mc-down').value);
var years = parseFloat(document.getElementById('mc-term').value);
var rate = parseFloat(document.getElementById('mc-rate').value);
var annualTax = parseFloat(document.getElementById('mc-tax').value);
var annualIns = parseFloat(document.getElementById('mc-insurance').value);
var monthlyHOA = parseFloat(document.getElementById('mc-hoa').value);
// 2. Validate inputs
if (isNaN(price) || isNaN(downPayment) || isNaN(years) || isNaN(rate)) {
alert("Please enter valid numbers for Price, Down Payment, Term, and Rate.");
return;
}
// Handle empty optional fields
if (isNaN(annualTax)) annualTax = 0;
if (isNaN(annualIns)) annualIns = 0;
if (isNaN(monthlyHOA)) monthlyHOA = 0;
// 3. Core Calculations
var principal = price – downPayment;
if (principal <= 0) {
alert("Down payment cannot be greater than or equal to the Home Price.");
return;
}
var monthlyInterestRate = (rate / 100) / 12;
var numberOfPayments = years * 12;
// Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPrincipalInterest = 0;
if (rate === 0) {
monthlyPrincipalInterest = principal / numberOfPayments;
} else {
var mathPower = Math.pow(1 + monthlyInterestRate, numberOfPayments);
monthlyPrincipalInterest = principal * ((monthlyInterestRate * mathPower) / (mathPower – 1));
}
// Secondary Costs
var monthlyTax = annualTax / 12;
var monthlyIns = annualIns / 12;
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyIns + monthlyHOA;
var totalCostOfLoan = (monthlyPrincipalInterest * numberOfPayments);
var totalInterestPaid = totalCostOfLoan – principal;
// 4. Update UI
// Helper function for currency formatting
function formatMoney(num) {
return "$" + num.toLocaleString('en-US', { minimumFractionDigits: 2, maximumFractionDigits: 2 });
}
document.getElementById('result-total-monthly').innerText = formatMoney(totalMonthlyPayment);
document.getElementById('result-pi').innerText = formatMoney(monthlyPrincipalInterest);
document.getElementById('result-tax').innerText = formatMoney(monthlyTax);
document.getElementById('result-ins').innerText = formatMoney(monthlyIns);
document.getElementById('result-total-interest').innerText = formatMoney(totalInterestPaid);
// Show results
document.getElementById('mc-results').style.display = 'block';
// Smooth scroll to results
document.getElementById('mc-results').scrollIntoView({ behavior: 'smooth' });
}