.calculator-wrapper {
max-width: 800px;
margin: 0 auto;
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
color: #333;
line-height: 1.6;
}
.calc-box {
background: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 30px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
margin-bottom: 40px;
}
.calc-title {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 24px;
font-weight: 700;
}
.input-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
margin-bottom: 25px;
}
@media (max-width: 600px) {
.input-grid {
grid-template-columns: 1fr;
}
}
.input-group {
display: flex;
flex-direction: column;
}
.input-group label {
font-size: 14px;
font-weight: 600;
margin-bottom: 8px;
color: #495057;
}
.input-group input {
padding: 12px;
border: 1px solid #ced4da;
border-radius: 4px;
font-size: 16px;
transition: border-color 0.2s;
}
.input-group input:focus {
border-color: #4CAF50;
outline: none;
}
.calc-btn {
width: 100%;
padding: 15px;
background-color: #4CAF50;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background-color 0.2s;
}
.calc-btn:hover {
background-color: #45a049;
}
.results-area {
margin-top: 30px;
padding-top: 20px;
border-top: 2px solid #e9ecef;
display: none;
}
.result-row {
display: flex;
justify-content: space-between;
margin-bottom: 10px;
font-size: 16px;
}
.result-row.main-result {
font-size: 24px;
font-weight: bold;
color: #2c3e50;
margin-top: 15px;
padding: 15px;
background: #e8f5e9;
border-radius: 4px;
}
.article-content h2 {
color: #2c3e50;
margin-top: 30px;
font-size: 22px;
}
.article-content p {
margin-bottom: 15px;
}
.article-content ul {
margin-bottom: 20px;
padding-left: 20px;
}
.article-content li {
margin-bottom: 8px;
}
function calculateCompoundInterest() {
// Get input values
var principal = parseFloat(document.getElementById('cic-principal').value);
var monthly = parseFloat(document.getElementById('cic-monthly').value);
var rate = parseFloat(document.getElementById('cic-rate').value);
var years = parseFloat(document.getElementById('cic-years').value);
// Validation: Ensure numbers are valid
if (isNaN(principal)) principal = 0;
if (isNaN(monthly)) monthly = 0;
if (isNaN(rate)) rate = 0;
if (isNaN(years)) years = 0;
// Basic Logic Validation
if (years < 0) {
alert("Years cannot be negative");
return;
}
// Calculation Constants
var n = 12; // Compounded monthly
var r = rate / 100;
var t = years;
var futureValue = 0;
var totalInvested = principal + (monthly * 12 * t);
// Formula Implementation
// A = P(1 + r/n)^(nt) + PMT * [((1 + r/n)^(nt) – 1) / (r/n)]
if (rate === 0) {
futureValue = totalInvested;
} else {
var compoundFactor = Math.pow(1 + (r/n), n*t);
// Future value of Initial Principal
var fvPrincipal = principal * compoundFactor;
// Future value of Monthly Contributions
var fvContributions = monthly * ((compoundFactor – 1) / (r/n));
futureValue = fvPrincipal + fvContributions;
}
var totalInterest = futureValue – totalInvested;
// Formatting Function
function formatMoney(amount) {
return "$" + amount.toLocaleString('en-US', {
minimumFractionDigits: 2,
maximumFractionDigits: 2
});
}
// Display Results
document.getElementById('res-principal').innerText = formatMoney(totalInvested);
document.getElementById('res-interest').innerText = formatMoney(totalInterest);
document.getElementById('res-total').innerText = formatMoney(futureValue);
// Show results container
document.getElementById('cic-results').style.display = 'block';
}
Compound Interest Calculator
Total Principal Invested:
–
Total Interest Earned:
–
Future Value:
–
Understanding Compound Interest
Compound interest is often referred to as the "eighth wonder of the world" because of its powerful ability to grow wealth over time. Unlike simple interest, which is calculated only on the principal amount, compound interest is calculated on the principal plus the accumulated interest from previous periods.
This creates a snowball effect: your money earns interest, and then that interest earns more interest. The longer you leave your money invested, the more dramatic the growth becomes.
How This Calculator Works
Our Compound Interest Calculator helps you project the future value of your investments based on four key factors:
- Initial Investment: The amount of money you start with (the principal).
- Monthly Contribution: Money added to the investment pool on a regular basis.
- Annual Interest Rate: The expected yearly return on your investment (e.g., 7-10% for stock market averages).
- Investment Period: How many years you plan to let the money grow.
Real-World Example
Let's look at a realistic scenario to illustrate the power of compounding:
Imagine you invest $5,000 initially and contribute $300 per month for 20 years at an average return of 8%.
- Your total out-of-pocket contribution would be: $77,000 ($5,000 + $300 × 12 months × 20 years).
- However, thanks to compound interest, your total investment value would grow to approximately $196,878.
- That means you earned nearly $120,000 purely in interest!
The Cost of Waiting
Time is the most critical factor in compound interest. Starting 5 years earlier can often double your returns, even if you invest less money overall. Use the calculator above to compare a 20-year timeline versus a 30-year timeline to see the massive difference a decade makes.