Estimate your monthly payments, interest, and total loan cost.
30 Years
20 Years
15 Years
10 Years
Monthly Principal & Interest:$0.00
Monthly Tax & Insurance & HOA:$0.00
Total Monthly Payment:$0.00
Total Interest Paid:$0.00
Total Cost of Loan:$0.00
function calculateMortgage() {
// Get Inputs
var homePrice = parseFloat(document.getElementById('mcHomePrice').value);
var downPayment = parseFloat(document.getElementById('mcDownPayment').value);
var years = parseInt(document.getElementById('mcTerm').value);
var ratePercent = parseFloat(document.getElementById('mcInterestRate').value);
var propTaxYear = parseFloat(document.getElementById('mcPropTax').value);
var insuranceYear = parseFloat(document.getElementById('mcInsurance').value);
var hoaMonth = parseFloat(document.getElementById('mcHOA').value);
// Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(years) || isNaN(ratePercent)) {
alert("Please enter valid numbers for Home Price, Down Payment, Term, and Interest Rate.");
return;
}
// Handle defaults for optional fields if empty/NaN
if (isNaN(propTaxYear)) propTaxYear = 0;
if (isNaN(insuranceYear)) insuranceYear = 0;
if (isNaN(hoaMonth)) hoaMonth = 0;
// Calculations
var principal = homePrice – downPayment;
if (principal <= 0) {
alert("Down payment cannot be greater than or equal to the home price.");
return;
}
var monthlyInterestRate = (ratePercent / 100) / 12;
var numberOfPayments = years * 12;
var monthlyPI = 0; // Principal and Interest
if (ratePercent === 0) {
monthlyPI = principal / numberOfPayments;
} else {
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
monthlyPI = principal * ( (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1) );
}
// Monthly Taxes, Insurance, HOA
var monthlyTax = propTaxYear / 12;
var monthlyInsurance = insuranceYear / 12;
var monthlyEscrow = monthlyTax + monthlyInsurance + hoaMonth;
var totalMonthlyPayment = monthlyPI + monthlyEscrow;
var totalCostOfLoan = (totalMonthlyPayment * numberOfPayments); // This is approximate if taxes change, but standard for calc
var totalInterestPaid = (monthlyPI * numberOfPayments) – principal;
// Total cost usually implies Total Principal + Total Interest + Total Escrow over life
// Re-adjusting Total Cost logic to be strictly Principal + Interest + Fees
var totalAmountPaidOverLife = (monthlyPI * numberOfPayments) + (monthlyEscrow * numberOfPayments);
// Update DOM
document.getElementById('resPI').innerHTML = "$" + monthlyPI.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resEscrow').innerHTML = "$" + monthlyEscrow.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resTotalMonthly').innerHTML = "$" + totalMonthlyPayment.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resTotalInterest').innerHTML = "$" + totalInterestPaid.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resTotalCost').innerHTML = "$" + totalAmountPaidOverLife.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
// Show Results
document.getElementById('mcResultBox').style.display = 'block';
}
Understanding Your Mortgage Calculation
Purchasing a home is likely the largest financial commitment you will make in your lifetime. Understanding the breakdown of your monthly mortgage payment is crucial for maintaining financial health. Our Mortgage Calculator goes beyond simple principal and interest calculations to give you a complete picture of your housing costs, including property taxes, homeowners insurance, and HOA fees.
How Is Your Monthly Mortgage Payment Calculated?
Your monthly payment is typically composed of four main parts, often referred to as PITI:
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 fixed-rate mortgage, the majority of your payment goes toward interest.
Taxes: Property taxes assessed by your local government. These are often collected by the lender and put into an escrow account to be paid annually.
Insurance: Homeowners insurance protects your property against damage. Like taxes, this is often paid through an escrow account.
The Impact of Interest Rates and Loan Terms
Even a small difference in your interest rate can result in tens of thousands of dollars in savings (or extra costs) over the life of a loan.
30-Year vs. 15-Year Terms: A 30-year mortgage offers lower monthly payments, making homes more affordable month-to-month, but you will pay significantly more in total interest. Conversely, a 15-year mortgage has higher monthly payments, but you build equity faster and pay far less interest overall.
What About HOA Fees?
If you are buying a condo, townhouse, or a home in a planned community, you will likely have to pay Homeowners Association (HOA) fees. While these are usually paid directly to the association and not the lender, they affect your Debt-to-Income (DTI) ratio and your overall monthly affordability. Our calculator includes an input for HOA fees to ensure your budget is realistic.
Tips for Lowering Your Mortgage Payment
If the result from the calculator is higher than your budget allows, consider the following strategies:
Increase your down payment: Putting 20% or more down eliminates Private Mortgage Insurance (PMI) and lowers the principal amount.
Shop for rates: Contact multiple lenders. A difference of 0.25% in interest rate can save you significant money.
Consider a longer term: Stretching the loan to 30 years lowers the monthly obligation, though it increases total cost.
Use this calculator as a starting point for your home buying journey. By adjusting the Home Price, Down Payment, and Interest Rate inputs, you can determine exactly how much house you can afford while maintaining a comfortable monthly budget.