#mortgage-calculator-app {
font-family: Arial, sans-serif;
max-width: 600px;
margin: 20px auto;
padding: 20px;
border: 1px solid #ddd;
border-radius: 8px;
box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}
#mortgage-calculator-app h2 {
text-align: center;
color: #333;
margin-bottom: 20px;
}
.calculator-input-group {
margin-bottom: 15px;
}
.calculator-input-group label {
display: block;
margin-bottom: 5px;
font-weight: bold;
color: #555;
}
.calculator-input-group input[type="number"],
.calculator-input-group input[type="text"],
.calculator-input-group select {
width: calc(100% – 22px);
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
}
.calculator-input-group input[type="number"]:focus,
.calculator-input-group input[type="text"]:focus,
.calculator-input-group select:focus {
border-color: #007bff;
outline: none;
}
.calculator-button {
display: block;
width: 100%;
padding: 12px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
cursor: pointer;
transition: background-color 0.3s ease;
}
.calculator-button:hover {
background-color: #0056b3;
}
#mortgage-result {
margin-top: 25px;
padding: 15px;
border-top: 1px solid #eee;
text-align: center;
font-size: 18px;
color: #333;
}
#mortgage-result p {
margin: 10px 0;
}
#mortgage-result .result-value {
font-weight: bold;
color: #28a745;
}
Understanding Your Mortgage Payment
A mortgage is a significant financial commitment, and understanding how your monthly payment is calculated is crucial for budgeting and financial planning. The primary components that determine your monthly mortgage payment (Principal and Interest) are the loan amount, the annual interest rate, and the loan term.
The Formula Explained
The standard formula for calculating the monthly payment (M) of a mortgage is:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
Where:
P = Principal loan amounti = Monthly interest rate (Annual interest rate divided by 12)n = Total number of payments (Loan term in years multiplied by 12)
Key Considerations:
- Principal (P): This is the actual amount of money you are borrowing from the lender.
- Interest Rate (i): This is the cost of borrowing money, expressed as a percentage. Lenders use the annual interest rate, but for the calculation, we need the monthly rate (annual rate / 12). A lower interest rate means a lower monthly payment and less interest paid over the life of the loan.
- Loan Term (n): This is the duration over which you will repay the loan. Common terms are 15 or 30 years. A shorter loan term results in higher monthly payments but less total interest paid. A longer term means lower monthly payments but significantly more interest paid over time.
This calculator focuses on the Principal and Interest (P&I) portion of your mortgage payment. Keep in mind that your actual monthly housing expense will likely be higher as it often includes property taxes, homeowner's insurance, and potentially Private Mortgage Insurance (PMI) or Homeowners Association (HOA) fees. These additional costs are referred to as 'escrow' or 'PITI' (Principal, Interest, Taxes, and Insurance).
function calculateMortgage() {
var loanAmount = parseFloat(document.getElementById("loanAmount").value);
var annualInterestRate = parseFloat(document.getElementById("annualInterestRate").value);
var loanTermYears = parseFloat(document.getElementById("loanTermYears").value);
var monthlyPaymentResultElement = document.getElementById("monthlyPaymentResult");
// Input validation
if (isNaN(loanAmount) || isNaN(annualInterestRate) || isNaN(loanTermYears) ||
loanAmount <= 0 || annualInterestRate <= 0 || loanTermYears <= 0) {
monthlyPaymentResultElement.innerHTML = "Please enter valid positive numbers for all fields.";
monthlyPaymentResultElement.style.color = "red";
return;
}
var monthlyInterestRate = annualInterestRate / 100 / 12;
var numberOfPayments = loanTermYears * 12;
// Mortgage payment formula
var monthlyPayment = loanAmount * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
// Format the result to two decimal places
var formattedMonthlyPayment = monthlyPayment.toFixed(2);
monthlyPaymentResultElement.innerHTML = "$" + formattedMonthlyPayment;
monthlyPaymentResultElement.style.color = "#28a745"; // Green color for positive result
}