Estimated APR
The calculated APR represents the annualized cost of borrowing, including interest and fees. A lower APR generally indicates a less expensive loan.
function calculateAPR() {
var loanAmount = parseFloat(document.getElementById("loanAmount").value);
var totalInterestPaid = parseFloat(document.getElementById("totalInterestPaid").value);
var loanTermInMonths = parseFloat(document.getElementById("loanTermInMonths").value);
var otherFees = parseFloat(document.getElementById("otherFees").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(loanAmount) || loanAmount <= 0 ||
isNaN(totalInterestPaid) || totalInterestPaid < 0 ||
isNaN(loanTermInMonths) || loanTermInMonths <= 0 ||
isNaN(otherFees) || otherFees < 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// Total cost of the loan = Principal + Total Interest + Other Fees
var totalCost = loanAmount + totalInterestPaid + otherFees;
// Approximate Annual Cost = Total Cost / Loan Term (in years)
var loanTermInYears = loanTermInMonths / 12;
var approximateAnnualCost = totalCost / loanTermInYears;
// APR is an approximation and for illustrative purposes.
// A more precise APR calculation often involves iterative methods
// to solve for the rate 'r' in the loan payment formula:
// P = L * [c(1 + c)^n] / [(1 + c)^n – 1] + F
// where P is total payment, L is loan principal, c is periodic rate (r/12), n is number of periods.
// For a simplified estimation here, we use the average annual cost relative to the principal.
var apr = (approximateAnnualCost – loanAmount) / loanAmount * 100;
// A more accurate estimation considering the total cost relative to the principal over the term, annualized.
// This is still a simplification of the true APR calculation which requires financial functions or iterative methods.
var totalFinanceCharge = totalInterestPaid + otherFees;
var effectiveAnnualRate = Math.pow((1 + (totalFinanceCharge / loanAmount) / loanTermInMonths), 12) – 1;
// We will display the simplified estimation for clarity based on the provided inputs.
// The simplified formula: APR ≈ (Total Interest Paid + Total Fees) / Loan Amount / Loan Term (in years) * 100
var simplifiedApr = ((totalInterestPaid + otherFees) / loanAmount) / loanTermInYears * 100;
if (loanAmount === 0) {
resultDiv.innerHTML = "Loan principal cannot be zero.";
return;
}
var finalAprToDisplay = simplifiedApr; // Using the simplified approximation
if (!isFinite(finalAprToDisplay) || finalAprToDisplay < 0) {
resultDiv.innerHTML = "Could not calculate APR with the provided values.";
} else {
resultDiv.innerHTML = finalAprToDisplay.toFixed(2) + "%";
}
}
.calculator-container {
font-family: sans-serif;
max-width: 600px;
margin: 20px auto;
padding: 20px;
border: 1px solid #ccc;
border-radius: 8px;
background-color: #f9f9f9;
}
.calculator-title {
text-align: center;
color: #333;
margin-bottom: 15px;
}
.calculator-description {
color: #555;
line-height: 1.6;
margin-bottom: 25px;
text-align: justify;
}
.form-group {
margin-bottom: 15px;
}
.form-group label {
display: block;
margin-bottom: 5px;
font-weight: bold;
color: #444;
}
.form-group input[type="number"] {
width: calc(100% – 22px);
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
}
.calculator-button {
display: block;
width: 100%;
padding: 12px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 16px;
transition: background-color 0.3s ease;
}
.calculator-button:hover {
background-color: #0056b3;
}
.calculator-result {
margin-top: 30px;
padding: 15px;
border-top: 1px solid #eee;
text-align: center;
}
.result-title {
color: #333;
margin-bottom: 10px;
}
#result {
font-size: 24px;
font-weight: bold;
color: #28a745;
margin-bottom: 10px;
}
.result-explanation {
font-size: 12px;
color: #777;
line-height: 1.4;
}