#mortgage-calculator-app {
font-family: sans-serif;
border: 1px solid #ccc;
padding: 20px;
border-radius: 8px;
max-width: 500px;
margin: 20px auto;
background-color: #f9f9f9;
}
#mortgage-calculator-app h2 {
text-align: center;
color: #333;
margin-bottom: 20px;
}
.input-group {
margin-bottom: 15px;
display: flex;
align-items: center;
}
.input-group label {
display: block;
margin-bottom: 5px;
color: #555;
width: 150px;
font-weight: bold;
}
.input-group input[type="number"],
.input-group input[type="range"] {
padding: 8px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box; /* Include padding and border in the element's total width and height */
flex-grow: 1; /* Allow input to grow and fill available space */
margin-left: 10px;
}
.input-group input[type="range"] {
margin-top: 5px; /* Add a bit of space between label and slider */
width: auto; /* Override default width for range */
flex-grow: 0; /* Prevent slider from growing */
min-width: 100px; /* Ensure slider has a minimum width */
}
button {
background-color: #4CAF50;
color: white;
padding: 10px 15px;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 16px;
width: 100%;
margin-top: 15px;
}
button:hover {
background-color: #45a049;
}
#result {
margin-top: 20px;
padding: 15px;
border: 1px solid #ddd;
border-radius: 4px;
background-color: #fff;
text-align: center;
font-size: 1.1em;
color: #333;
}
#result span {
font-weight: bold;
color: #4CAF50;
}
#calculator-description {
margin-top: 30px;
padding: 15px;
border-top: 1px solid #eee;
line-height: 1.6;
color: #444;
}
#calculator-description h3 {
margin-top: 0;
color: #333;
}
Understanding Your Mortgage Payment
A mortgage is a type of loan used to purchase real estate, typically a home. The mortgage payment is the regular amount you pay to your lender to repay the loan. This payment is usually made monthly and includes several components, primarily covering the principal and interest. Over time, the portion of your payment that goes towards the principal increases, while the interest portion decreases.
Key Components of Your Mortgage Calculation:
- Loan Amount: This is the total sum of money you borrow from the lender to buy your home. It's the purchase price of the property minus your down payment.
- Annual Interest Rate: This is the percentage charged by the lender for borrowing the money. It's crucial to understand that this is an annual rate, and your monthly payment will be based on a fraction of this rate.
- Loan Term (in Years): This is the total duration over which you agree to repay the mortgage loan. Common terms are 15 or 30 years. A shorter term means higher monthly payments but less total interest paid over the life of the loan.
The Monthly Payment Formula (Amortization):
The standard formula used to calculate the fixed monthly payment (M) for a mortgage is:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
Where:
- P = Principal loan amount
- i = Monthly interest rate (annual rate divided by 12)
- n = Total number of payments (loan term in years multiplied by 12)
This calculator uses this formula to provide an estimate of your principal and interest payment. Remember that your actual total monthly housing expense may also include property taxes, homeowner's insurance, and potentially private mortgage insurance (PMI) or HOA fees, which are not included in this calculation.
Example Calculation:
Let's consider a mortgage with:
- Loan Amount (P): $300,000
- Annual Interest Rate: 3.75%
- Loan Term: 30 years
First, we calculate the monthly interest rate (i) and the total number of payments (n):
- Monthly interest rate (i) = 3.75% / 12 = 0.0375 / 12 = 0.003125
- Total number of payments (n) = 30 years * 12 months/year = 360
Plugging these values into the formula:
M = 300,000 [ 0.003125(1 + 0.003125)^360 ] / [ (1 + 0.003125)^360 – 1]
This calculation results in a monthly payment (M) of approximately $1,391.88.
function calculateMortgage() {
var principal = parseFloat(document.getElementById("loanAmount").value);
var annualRate = parseFloat(document.getElementById("interestRate").value);
var loanTermYears = parseFloat(document.getElementById("loanTerm").value);
if (isNaN(principal) || isNaN(annualRate) || isNaN(loanTermYears) || principal <= 0 || annualRate < 0 || loanTermYears <= 0) {
document.getElementById("result").innerHTML = "Please enter valid numbers for all fields.";
return;
}
var monthlyRate = annualRate / 100 / 12;
var numberOfPayments = loanTermYears * 12;
var monthlyPayment = principal * (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
if (isNaN(monthlyPayment) || !isFinite(monthlyPayment)) {
document.getElementById("result").innerHTML = "Calculation resulted in an invalid number. Please check your inputs.";
return;
}
document.getElementById("result").innerHTML = "Your estimated monthly mortgage payment will be: