Investment Growth Calculator
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Your Investment Projection
Understanding Investment Growth
This Investment Growth Calculator helps you visualize the potential power of compounding over time. By inputting your initial investment, regular contributions, expected annual growth rate, and the investment horizon, you can get an estimate of your investment's future value.
How the Calculation Works
The calculator uses a compound interest formula adapted to include regular contributions. The core formula for compound interest is:
FV = PV * (1 + r)^n
Where:
FV is the Future ValuePV is the Present Value (Initial Investment)r is the periodic interest rate (annual growth rate in this case)n is the number of periods (investment years)
However, to account for annual contributions, a more complex formula is used, essentially summing up the future value of the initial investment and the future value of an annuity (the series of annual contributions).
The simplified approach employed here iteratively calculates the value year by year, adding the annual contribution at the end of each period and then applying the growth rate. For a more precise financial calculation, especially with contributions at the start of the period or different compounding frequencies, more advanced formulas are used, but this provides a very good approximation.
The formula used in this calculator conceptually represents:
Total Future Value = Future Value of Initial Investment + Future Value of Annual Contributions
The calculation in the script iteratively applies the growth and adds contributions.
Key Inputs Explained
- Initial Investment: The lump sum amount you are starting with.
- Annual Contribution: The amount you plan to add to your investment each year. This is crucial for long-term growth and can significantly boost your final amount.
- Annual Growth Rate (%): This is your expected average annual return on investment, expressed as a percentage. It's important to be realistic; historical market averages can be a guide, but past performance is not indicative of future results.
- Investment Duration (Years): The length of time you plan to keep your money invested. The longer your money is invested, the more time compounding has to work its magic.
Why Use This Calculator?
- Financial Planning: Helps set realistic goals for retirement, down payments, or other long-term objectives.
- Understanding Compounding: Demonstrates the power of "interest on interest" and how time and consistent contributions amplify growth.
- Evaluating Scenarios: Easily compare how different growth rates or contribution amounts might impact your final outcome.
- Motivation: Seeing the potential future value can be a strong motivator to start investing or to continue contributing regularly.
Disclaimer: This calculator provides an estimate for educational purposes only. It does not constitute financial advice. Investment returns are not guaranteed, and the value of investments can fluctuate. Consult with a qualified financial advisor before making any investment decisions.
function calculateGrowth() {
var initialInvestment = parseFloat(document.getElementById("initialInvestment").value);
var annualContribution = parseFloat(document.getElementById("annualContribution").value);
var annualGrowthRate = parseFloat(document.getElementById("annualGrowthRate").value) / 100; // Convert percentage to decimal
var investmentYears = parseInt(document.getElementById("investmentYears").value);
var resultValueElement = document.getElementById("result-value");
// Input validation
if (isNaN(initialInvestment) || isNaN(annualContribution) || isNaN(annualGrowthRate) || isNaN(investmentYears) ||
initialInvestment < 0 || annualContribution < 0 || annualGrowthRate < -1 || investmentYears <= 0) {
resultValueElement.textContent = "Invalid Input";
return;
}
var currentValue = initialInvestment;
// Iterative calculation for each year
for (var i = 0; i < investmentYears; i++) {
// Add annual contribution (assuming it's added at the end of the year for simplicity)
currentValue += annualContribution;
// Apply growth for the year
currentValue *= (1 + annualGrowthRate);
}
// Format the result to two decimal places and add appropriate currency formatting
var formattedResult = currentValue.toLocaleString(undefined, {
style: 'currency',
currency: 'USD' // Default currency, can be made dynamic if needed
});
resultValueElement.textContent = formattedResult;
}