Calculate how your savings can grow over time with compound interest.
Monthly
Annually
Quarterly
Daily
Please enter valid numeric values for all fields.
Projection Results
Future Value:–
Total Principal Invested:–
Total Interest Earned:–
Understanding Investment Growth and Compound Interest
Investing is one of the most effective ways to build wealth over time. Unlike simple savings, where your money sits idle, investing allows your capital to generate returns. The true power behind this growth is compound interest.
What is Compound Interest?
Compound interest is the concept of earning "interest on interest." When you invest money, any returns earned are reinvested to generate their own returns. Over long periods, this creates a snowball effect that can significantly increase the value of your portfolio.
For example, if you invest $10,000 at a 7% annual return:
In Year 1, you earn $700.
In Year 2, you earn 7% on $10,700 (your principal + Year 1 interest), which is $749.
By Year 30, that initial $10,000 could grow to over $76,000 without adding another penny.
Key Factors Affecting Your Investment
Using the Investment Growth Calculator above, you can manipulate several variables to see how they impact your financial future:
Initial Deposit: The starting lump sum gives your investment a head start. The larger the initial amount, the more base capital you have compounding immediately.
Monthly Contribution: Consistency is key. Even small monthly additions can drastically reduce the time it takes to reach your financial goals. Dollar-cost averaging (investing a fixed amount regularly) also helps mitigate market volatility.
Interest Rate: This is your rate of return. While the stock market historically averages around 7-10% annually (adjusted for inflation), safer investments like bonds or HYSAs offer lower rates. A difference of just 1-2% can result in tens of thousands of dollars difference over 20+ years.
Time Horizon: Time is the most critical component. The longer your money remains invested, the more powerful the compounding effect becomes. Starting 5 years earlier can sometimes be more beneficial than doubling your monthly contributions later.
How to Use This Calculator
This tool is designed to help you visualize your potential returns. Simply enter your current savings (Initial Deposit), how much you plan to save each month, the expected annual return rate, and how many years you plan to let the money grow. The calculator uses the standard compound interest formula to project your future wealth.
function calculateInvestment() {
// Get input values
var initialDeposit = parseFloat(document.getElementById("initialDeposit").value);
var monthlyContribution = parseFloat(document.getElementById("monthlyContribution").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var years = parseFloat(document.getElementById("investmentYears").value);
var compoundFreq = parseInt(document.getElementById("compoundFreq").value);
// Validation
var errorDiv = document.getElementById("errorMsg");
var resultDiv = document.getElementById("result");
if (isNaN(initialDeposit) || isNaN(monthlyContribution) || isNaN(interestRate) || isNaN(years)) {
errorDiv.style.display = "block";
resultDiv.style.display = "none";
return;
}
errorDiv.style.display = "none";
// Logic
// Formula for Future Value of a Lump Sum: P * (1 + r/n)^(nt)
// Formula for Future Value of a Series: PMT * (((1 + r/n)^(nt) – 1) / (r/n))
var r = interestRate / 100;
var n = compoundFreq;
var t = years;
// Calculate Future Value of Initial Deposit
var fvLumpSum = initialDeposit * Math.pow((1 + r/n), (n * t));
// Calculate Future Value of Contributions
// Note: Contributions are usually monthly. If compound freq != 12, this gets complex.
// For simplicity in this specific calculator, we assume contributions match the compounding frequency
// or we simplify. However, usually contributions are monthly.
// To be precise: If contributions are monthly but compounding is different, we adjust the rate.
// Let's assume standard PMT formula where contributions happen at the END of each period defined by n.
// To make it user-friendly for "Monthly Contribution" regardless of compound freq:
var totalPrincipal = initialDeposit + (monthlyContribution * 12 * t);
var fv contributions = 0;
// Iterative approach for accuracy with monthly contributions regardless of compound frequency
var currentBalance = initialDeposit;
var monthlyRate = r / 12; // Simple monthly rate approximation for accumulation steps
// However, the standard formula is best. Let's align contributions to monthly.
// If compounding is not monthly, we calculate effective rate.
// Let's stick to a robust iterative loop to handle "Monthly Contribution" correctly against any "Compound Frequency"
var totalMonths = t * 12;
var balance = initialDeposit;
for (var i = 1; i <= totalMonths; i++) {
// Add monthly contribution
balance += monthlyContribution;
// Apply interest if it's a compounding period
// e.g. if n=12 (monthly), apply every month. if n=1 (yearly), apply every 12th month.
// Using fractional compounding for smoother calculation is standard in finance,
// but simple compounding applies at discrete intervals.
// Let's use the precise mathematical formula for monthly contributions with n-compounding:
// This is complex. Let's switch to the standard assumption:
// If user selects Monthly compounding, it aligns.
// If Daily, it compounds daily.
// Standard approach: FV = FV(Lump) + FV(Annuity)
// We need to convert annual rate to monthly rate for the annuity part if n=12.
}
// Re-simplifying for robustness:
// We will treat the Monthly Contribution as an annuity.
// We assume Compounding Frequency = Payment Frequency for the annuity part to keep it standard,
// OR we just convert everything to monthly for the "Monthly Contribution" input context.
// Most users expect monthly compounding for monthly contributions.
// Let's use the loop for absolute clarity and correctness.
balance = initialDeposit;
var dailyRate = r / 365;
// We will simulate day by day? No, too slow for long periods. Month by month.
// Let's use the detailed formula:
// FV = P * (1 + r/n)^(n*t) + PMT * ( ((1 + r/n)^(n*t) – 1) / (r/n) )
// This formula assumes PMT is made every 'n' period.
// But our input is "Monthly".
if (compoundFreq === 12) {
// Periods match
fvContributions = monthlyContribution * ( (Math.pow(1 + r/12, 12*t) – 1) / (r/12) );
fvLumpSum = initialDeposit * Math.pow(1 + r/12, 12*t);
balance = fvLumpSum + fvContributions;
} else {
// Mismatch case (e.g. Monthly deposit, Daily compounding)
// We fall back to a monthly iteration adding interest based on effective rate
balance = initialDeposit;
for (var m = 0; m < totalMonths; m++) {
// Add contribution at end of month
// Calculate interest for this month
// Effective monthly rate from annual rate with n compounding:
// (1 + r/n)^(n/12) – 1
var effectiveMonthlyRate = Math.pow((1 + r/n), (n/12)) – 1;
balance = balance * (1 + effectiveMonthlyRate) + monthlyContribution;
}
}
var futureValue = balance;
var totalInterest = futureValue – totalPrincipal;
// Formatting currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2,
maximumFractionDigits: 2,
});
// Display results
document.getElementById("resFutureValue").innerHTML = formatter.format(futureValue);
document.getElementById("resTotalPrincipal").innerHTML = formatter.format(totalPrincipal);
document.getElementById("resTotalInterest").innerHTML = formatter.format(totalInterest);
document.getElementById("result").style.display = "block";
}