A mortgage is a significant financial commitment, and understanding your potential monthly payments is crucial for budgeting and making informed decisions. This calculator helps estimate your monthly mortgage payment based on the home price, your down payment, the annual interest rate, and the loan term.
How it works:
Home Price: The total advertised price of the property you are considering.
Down Payment: The upfront amount of cash you pay towards the home's purchase. A larger down payment reduces the amount you need to borrow.
Annual Interest Rate: The yearly cost of borrowing money, expressed as a percentage. This rate depends on market conditions and your creditworthiness.
Loan Term: The total number of years you have to repay the loan. Common terms are 15, 20, or 30 years. Shorter terms mean higher monthly payments but less interest paid over time.
The calculator uses the standard mortgage payment formula (M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]), where:
M = Monthly Payment
P = Principal Loan Amount (Home Price – Down Payment)
n = Total Number of Payments (Loan Term in Years * 12)
Note: This calculation provides an estimate of the principal and interest portion of your mortgage payment only. It does not include property taxes, homeowner's insurance (often called PITI – Principal, Interest, Taxes, and Insurance), or potential Private Mortgage Insurance (PMI), which can significantly increase your total monthly housing cost.
function calculateMortgage() {
var homePrice = parseFloat(document.getElementById("homePrice").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTerm = parseFloat(document.getElementById("loanTerm").value);
if (isNaN(homePrice) || homePrice <= 0) {
alert("Please enter a valid Home Price.");
return;
}
if (isNaN(downPayment) || downPayment < 0) {
alert("Please enter a valid Down Payment.");
return;
}
if (isNaN(interestRate) || interestRate <= 0) {
alert("Please enter a valid Annual Interest Rate.");
return;
}
if (isNaN(loanTerm) || loanTerm <= 0) {
alert("Please enter a valid Loan Term.");
return;
}
var loanAmount = homePrice – downPayment;
if (loanAmount <= 0) {
document.getElementById("monthlyPayment").textContent = "$0.00";
document.getElementById("loanAmountDisplay").textContent = "Loan Amount: $0.00 (No loan required)";
return;
}
var monthlyInterestRate = (interestRate / 100) / 12;
var numberOfPayments = loanTerm * 12;
var monthlyPayment = loanAmount * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
document.getElementById("monthlyPayment").textContent = "$" + monthlyPayment.toFixed(2);
document.getElementById("loanAmountDisplay").textContent = "Loan Amount: $" + loanAmount.toFixed(2);
}