Estimate your monthly mortgage payments including interest and principal.
Monthly Principal & Interest:$0.00
Total Loan Amount:$0.00
Total Interest Paid:$0.00
Total Cost of Loan:$0.00
Understanding Your Mortgage Payments
Buying a home is one of the most significant financial decisions you'll ever make. Using a mortgage payment calculator helps you understand the long-term commitment of a home loan. The monthly payment consists of several components, primarily the principal repayment and the interest charged by the lender.
How the Calculation Works
The formula for calculating the monthly payment (M) is:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
P: The principal loan amount (Home price minus down payment).
i: The monthly interest rate (Annual rate divided by 12).
n: The total number of months (Years multiplied by 12).
Real-World Example
If you purchase a home for $350,000 with a $70,000 down payment (20%), your loan amount is $280,000. At a 7% interest rate over 30 years, your monthly principal and interest payment would be approximately $1,862.84. Over the life of the loan, you would pay a total of $390,622 in interest alone.
Factors That Affect Your Payment
Several variables can change your actual monthly out-of-pocket costs:
Property Taxes: Usually assessed annually by your local government and often rolled into your monthly mortgage payment via escrow.
Homeowners Insurance: Required by lenders to protect the asset against damage.
Private Mortgage Insurance (PMI): Usually required if your down payment is less than 20% of the home's value.
HOA Fees: Fees paid to a Homeowners Association for community maintenance.
function calculateMortgage() {
var homePrice = parseFloat(document.getElementById("homePrice").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var annualRate = parseFloat(document.getElementById("interestRate").value);
var years = parseFloat(document.getElementById("loanTerm").value);
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(annualRate) || isNaN(years) || homePrice <= 0) {
alert("Please enter valid positive numbers for all fields.");
return;
}
var principal = homePrice – downPayment;
if (principal <= 0) {
alert("Down payment cannot be greater than or equal to the home price.");
return;
}
var monthlyRate = (annualRate / 100) / 12;
var numberOfPayments = years * 12;
var monthlyPayment = 0;
if (monthlyRate === 0) {
monthlyPayment = principal / numberOfPayments;
} else {
var x = Math.pow(1 + monthlyRate, numberOfPayments);
monthlyPayment = (principal * x * monthlyRate) / (x – 1);
}
var totalCost = monthlyPayment * numberOfPayments;
var totalInterest = totalCost – principal;
document.getElementById("monthlyPaymentDisplay").innerText = "$" + monthlyPayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("totalLoanDisplay").innerText = "$" + principal.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("totalInterestDisplay").innerText = "$" + totalInterest.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("totalCostDisplay").innerText = "$" + totalCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById("mortgageResult").style.display = "block";
}