.cic-wrapper {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 0 auto;
padding: 20px;
color: #333;
line-height: 1.6;
}
.cic-calculator-box {
background: #ffffff;
border: 1px solid #e0e0e0;
border-radius: 8px;
padding: 30px;
box-shadow: 0 4px 12px rgba(0,0,0,0.05);
margin-bottom: 40px;
}
.cic-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
@media (max-width: 600px) {
.cic-grid {
grid-template-columns: 1fr;
}
}
.cic-input-group {
margin-bottom: 15px;
}
.cic-input-group label {
display: block;
font-weight: 600;
margin-bottom: 8px;
font-size: 14px;
color: #2c3e50;
}
.cic-input-wrapper {
position: relative;
display: flex;
align-items: center;
}
.cic-prefix, .cic-suffix {
background: #f4f6f8;
border: 1px solid #d1d5db;
padding: 10px 15px;
color: #555;
font-size: 14px;
}
.cic-prefix {
border-right: none;
border-radius: 6px 0 0 6px;
}
.cic-suffix {
border-left: none;
border-radius: 0 6px 6px 0;
}
.cic-input {
width: 100%;
padding: 10px;
border: 1px solid #d1d5db;
font-size: 16px;
outline: none;
transition: border-color 0.2s;
}
.cic-input.has-prefix { border-radius: 0 6px 6px 0; }
.cic-input.has-suffix { border-radius: 6px 0 0 6px; }
.cic-input:focus {
border-color: #2271b1;
z-index: 2;
}
.cic-btn {
background-color: #2271b1;
color: white;
border: none;
padding: 15px 30px;
font-size: 16px;
font-weight: bold;
border-radius: 6px;
cursor: pointer;
width: 100%;
margin-top: 10px;
transition: background-color 0.2s;
}
.cic-btn:hover {
background-color: #135e96;
}
.cic-results {
background: #f8f9fa;
border-radius: 8px;
padding: 25px;
margin-top: 30px;
display: none;
border-left: 5px solid #2271b1;
}
.cic-result-row {
display: flex;
justify-content: space-between;
margin-bottom: 12px;
padding-bottom: 12px;
border-bottom: 1px solid #e9ecef;
}
.cic-result-row:last-child {
border-bottom: none;
margin-bottom: 0;
padding-bottom: 0;
}
.cic-result-label {
color: #555;
font-size: 15px;
}
.cic-result-value {
font-weight: 700;
font-size: 18px;
color: #333;
}
.cic-total-value {
font-size: 24px;
color: #2271b1;
}
.cic-article h2 {
font-size: 24px;
margin-top: 40px;
margin-bottom: 20px;
color: #2c3e50;
border-bottom: 2px solid #eee;
padding-bottom: 10px;
}
.cic-article h3 {
font-size: 20px;
margin-top: 30px;
margin-bottom: 15px;
color: #34495e;
}
.cic-article p {
margin-bottom: 15px;
color: #4a5568;
}
.cic-article ul {
margin-bottom: 20px;
padding-left: 20px;
}
.cic-article li {
margin-bottom: 10px;
color: #4a5568;
}
.cic-error {
color: #dc3232;
font-size: 14px;
margin-top: 10px;
display: none;
}
function calculateCompoundInterest() {
// Get input values using var
var initialInput = document.getElementById('cic_initial');
var monthlyInput = document.getElementById('cic_monthly');
var rateInput = document.getElementById('cic_rate');
var yearsInput = document.getElementById('cic_years');
var errorDiv = document.getElementById('cic_error');
var resultDiv = document.getElementById('cic_results');
// Parse values
var P = parseFloat(initialInput.value);
var PMT = parseFloat(monthlyInput.value);
var R = parseFloat(rateInput.value);
var t = parseFloat(yearsInput.value);
// Reset error state
errorDiv.style.display = 'none';
resultDiv.style.display = 'none';
// Validation
if (isNaN(P) || P < 0) P = 0;
if (isNaN(PMT) || PMT < 0) PMT = 0;
// Rate and Years are strictly required for calculation
if (isNaN(R) || isNaN(t) || t <= 0) {
errorDiv.style.display = 'block';
errorDiv.innerHTML = "Please enter a valid interest rate and time period (years).";
return;
}
// Calculation Logic
// Formula: FV = P * (1 + r/n)^(nt) + PMT * [ (1 + r/n)^(nt) – 1 ] / (r/n)
// n = 12 (Monthly compounding)
var n = 12;
var r = R / 100;
var totalMonths = t * n;
// Future Value of Initial Lump Sum
var fvLumpSum = P * Math.pow((1 + r/n), totalMonths);
// Future Value of Monthly Contributions
var fvSeries = 0;
if (r === 0) {
fvSeries = PMT * totalMonths;
} else {
fvSeries = PMT * (Math.pow((1 + r/n), totalMonths) – 1) / (r/n);
}
var totalFV = fvLumpSum + fvSeries;
var totalPrincipal = P + (PMT * totalMonths);
var totalInterest = totalFV – totalPrincipal;
// Formatting functions
function formatMoney(amount) {
return '$' + amount.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}
// Output Results
document.getElementById('cic_output_fv').innerHTML = formatMoney(totalFV);
document.getElementById('cic_output_principal').innerHTML = formatMoney(totalPrincipal);
document.getElementById('cic_output_interest').innerHTML = formatMoney(totalInterest);
// Show result box
resultDiv.style.display = 'block';
}
Investment Returns Calculator
$
$
%
Years
Please enter valid positive numbers for all fields.
Future Investment Value:
$0.00
Total Principal Invested:
$0.00
Total Interest Earned:
$0.00
Understanding Compound Interest & Investment Growth
When planning for long-term financial goals—whether it's retirement, a child's education, or buying a home—understanding how your money grows is crucial. This calculator uses the power of compound interest to project the future value of your investments.
How Does This Calculator Work?
This tool calculates the future value of an investment series based on four key variables:
- Initial Investment: The lump sum of money you start with today.
- Monthly Contribution: The amount you add to your investment portfolio every month. Regular contributions are the engine of wealth building.
- Annual Interest Rate: The expected yearly return on your investment. For example, the S&P 500 has historically returned about 10% annually (before inflation), while savings accounts typically offer lower rates.
- Investment Period: The number of years you plan to let the money grow.
The Magic of Compounding
Albert Einstein reportedly called compound interest the "eighth wonder of the world." Unlike simple interest, where you only earn money on your principal, compound interest means you earn interest on your interest.
For example, if you invest $10,000 at a 7% return:
- In Year 1, you earn $700. Balance: $10,700.
- In Year 2, you earn 7% on $10,700 (which is $749). Balance: $11,449.
- By Year 30, that same 7% growth generates over $5,000 in a single year, even if you never added another penny.
Realistic Return Expectations
When estimating your interest rate input, consider your asset class:
- High Yield Savings / CDs: 2% – 5% (Low Risk)
- Bonds: 4% – 6% (Moderate Risk)
- Stock Market Index Funds: 7% – 10% (Higher Risk, Long Term)
- Real Estate: 8% – 12% (Varies widely)
Note: Inflation typically reduces purchasing power by 2-3% annually, so consider using a "real" return rate (Nominal Rate minus Inflation) for more conservative planning.