Compound Interest Calculator
Discover the power of compound interest. See how your investments can grow exponentially over time with our free, interactive calculator.
The amount you're starting with
Amount you'll add every month
$302,370.09
$130,000.00
$172,370.09
Watch your money snowball with compound interest
Starting Amount
$10,000.00
Total Monthly Added
$120,000.00
Interest as % of Total
57.0%
Growth Multiple
2.33x
How to Use This Calculator
Enter Your Initial Investment
Start with the amount you have available to invest today. This is your starting principal.
Set Monthly Contributions
Add how much you plan to contribute each month. Even small regular contributions can make a huge difference.
Adjust the Interest Rate
Use the slider to set your expected annual return. Historical stock market returns average around 7-10% per year.
Choose Your Time Horizon
Select how many years you plan to invest. The longer your time horizon, the more powerful compound interest becomes.
What is Compound Interest?
Compound interest is often called the "eighth wonder of the world" — and for good reason. It's the process where the interest you earn on an investment also earns interest, creating a snowball effect that accelerates your wealth growth over time.
Unlike simple interest, which only calculates interest on your original principal, compound interest calculates interest on both your principal AND your accumulated interest from previous periods.
Year 1
Interest earned on your principal only
Year 10
Interest earned on principal + 9 years of interest
Year 30
The majority of your balance is from interest
The Rule of 72
The Rule of 72 is a simple formula to estimate how long it will take for your investment to double at a given interest rate:
Years to Double = 72 ÷ Interest Rate
At 4%
18 years
At 6%
12 years
At 8%
9 years
At 10%
7.2 years
Educational Disclaimer
Important: This calculator is provided for educational and illustrative purposes only. The results are hypothetical and do not guarantee any specific investment outcome.
- Actual investment returns vary and can be negative. Past performance does not guarantee future results.
- This calculator does not account for taxes, fees, inflation, or other factors that may affect your actual returns.
- The interest rate used is a simplified annual rate. Real investments may compound at different frequencies and rates.
- This tool does not constitute financial advice. Please consult with a qualified financial advisor before making investment decisions.
Pro Portfolio Tracker does not hold an Australian Financial Services Licence (AFSL) and is not authorised to provide personal financial advice.
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