Please enter valid positive numbers for Home Price, Down Payment, and Interest Rate.
Estimated Monthly Payment
Principal & Interest:$0.00
Property Tax (Monthly):$0.00
Home Insurance (Monthly):$0.00
HOA Fees:$0.00
Total Monthly Payment:$0.00
Total Loan Amount:$0.00
Total Interest Paid:$0.00
Payoff Date:–
function calculateMortgage() {
// Get Input Elements
var homePriceInput = document.getElementById('homePrice');
var downPaymentInput = document.getElementById('downPayment');
var interestRateInput = document.getElementById('interestRate');
var loanTermInput = document.getElementById('loanTerm');
var propertyTaxInput = document.getElementById('propertyTax');
var homeInsuranceInput = document.getElementById('homeInsurance');
var hoaFeesInput = document.getElementById('hoaFees');
// Get Values
var price = parseFloat(homePriceInput.value);
var down = parseFloat(downPaymentInput.value);
var rate = parseFloat(interestRateInput.value);
var termYears = parseInt(loanTermInput.value);
var taxYear = parseFloat(propertyTaxInput.value) || 0;
var insYear = parseFloat(homeInsuranceInput.value) || 0;
var hoaMonth = parseFloat(hoaFeesInput.value) || 0;
var errorMsg = document.getElementById('errorMessage');
var resultsDiv = document.getElementById('calc-results');
// Validation
if (isNaN(price) || isNaN(down) || isNaN(rate) || price <= 0 || rate = price) {
errorMsg.innerText = "Down payment cannot be greater than or equal to Home Price.";
errorMsg.style.display = 'block';
resultsDiv.style.display = 'none';
return;
} else {
errorMsg.innerText = "Please enter valid positive numbers for Home Price, Down Payment, and Interest Rate.";
errorMsg.style.display = 'none';
}
// Calculations
var loanAmount = price – down;
var monthlyRate = (rate / 100) / 12;
var totalPayments = termYears * 12;
// Amortization Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPrincipalInterest = 0;
if (rate > 0) {
var x = Math.pow(1 + monthlyRate, totalPayments);
monthlyPrincipalInterest = loanAmount * ((monthlyRate * x) / (x – 1));
} else {
monthlyPrincipalInterest = loanAmount / totalPayments;
}
var monthlyTax = taxYear / 12;
var monthlyIns = insYear / 12;
var totalMonthly = monthlyPrincipalInterest + monthlyTax + monthlyIns + hoaMonth;
var totalCost = (monthlyPrincipalInterest * totalPayments);
var totalInterest = totalCost – loanAmount;
// Calculate Payoff Date
var today = new Date();
today.setFullYear(today.getFullYear() + termYears);
var options = { month: 'long', year: 'numeric' };
var payoffDate = today.toLocaleDateString("en-US", options);
// Formatting
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
});
// Display Results
document.getElementById('resPrincipalInterest').innerText = formatter.format(monthlyPrincipalInterest);
document.getElementById('resTax').innerText = formatter.format(monthlyTax);
document.getElementById('resInsurance').innerText = formatter.format(monthlyIns);
document.getElementById('resHOA').innerText = formatter.format(hoaMonth);
document.getElementById('resTotalMonthly').innerText = formatter.format(totalMonthly);
document.getElementById('resLoanAmount').innerText = formatter.format(loanAmount);
document.getElementById('resTotalInterest').innerText = formatter.format(totalInterest);
document.getElementById('resPayoffDate').innerText = payoffDate;
resultsDiv.style.display = 'block';
}
How to Calculate Your Mortgage Payment
Buying a home is one of the most significant financial decisions you will make in your lifetime. Understanding how your monthly mortgage payment is calculated is essential for budgeting and determining how much house you can afford. This Mortgage Payment Calculator helps you estimate your monthly financial commitment by breaking down the costs associated with a home loan.
Did You Know? Your monthly mortgage payment consists of more than just paying back the money you borrowed. It typically includes Principal, Interest, Taxes, and Insurance (often referred to as PITI).
Understanding the Key Components
To accurately use this calculator, it helps to understand the different variables that impact your monthly payment:
Principal: This is the portion of your payment that goes toward paying down the loan balance (the amount you borrowed).
Interest: This is the cost of borrowing money, paid to the lender. In the early years of a mortgage, a larger portion of your payment goes toward interest.
Property Taxes: Local governments assess taxes on property to fund public services. These are often collected by the lender in an escrow account and paid annually on your behalf.
Homeowners Insurance: Lenders require insurance to protect the home against damage. Like taxes, this is often paid monthly into an escrow account.
HOA Fees: If you buy a condo or a home in a planned community, you may have to pay Homeowners Association fees. These are usually paid directly to the HOA but affect your total monthly housing cost.
The Mortgage Formula
While this calculator handles the math for you instantly, the standard formula used to calculate the monthly principal and interest payment is:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
Where:
M = Total monthly payment
P = Principal loan amount (Home Price minus Down Payment)
i = Monthly interest rate (Annual rate divided by 12)
n = Number of payments (Loan term in years multiplied by 12)
How Interest Rates Affect Affordability
Even a small difference in interest rates can have a massive impact on your monthly payment and the total interest paid over the life of the loan. For example, on a $300,000 loan, the difference between a 6% and a 7% interest rate can change your monthly payment by nearly $200 and cost you tens of thousands of dollars more over 30 years.
Tips for Lowering Your Mortgage Payment
If the estimated payment is higher than your budget allows, consider these strategies:
Increase your down payment: Putting more money down reduces the principal loan amount.
Improve your credit score: Higher credit scores often qualify for lower interest rates.
Shop around: Compare rates from different lenders to find the best deal.
Consider a longer term: While a 30-year loan means paying more interest over time compared to a 15-year loan, the monthly payments are significantly lower.