📈 Investment Details
Enter your investment details to see your money grow
💰 Your Investment Results
📊 Growth Over Time
📅 Year-by-Year Growth
| Year | Balance Start | Contributions | Interest Earned | End Balance | Growth |
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What is Compound Interest?
Compound interest is the process where interest is earned not only on your initial principal but also on the accumulated interest from previous periods. Often called the eighth wonder of the world, compound interest is the most powerful force in building long-term wealth. The longer your money compounds, the faster it grows.
Our free compound interest calculator shows you exactly how your money grows year by year — whether you are investing in a savings account, index fund, retirement account, or any other interest-bearing investment.
Compound Interest Formula
The standard compound interest formula used in our calculator is:
Daily vs Monthly vs Annual Compounding
The more frequently interest compounds, the more you earn. Daily compounding produces slightly higher returns than monthly, which produces more than annual. Our calculator lets you compare all frequencies so you can see the exact difference for your investment.
The Rule of 72 — How Fast Will Your Money Double?
The Rule of 72 is a simple way to estimate how long it takes for your investment to double. Simply divide 72 by your annual interest rate. At 7% annual return, your money doubles approximately every 10.3 years. At 10%, it doubles every 7.2 years. Our calculator shows you this automatically.
How to Maximize Compound Interest
- Start investing as early as possible — time is the most powerful variable in compound interest
- Reinvest all earnings rather than withdrawing interest
- Make regular monthly contributions to accelerate growth dramatically
- Choose accounts with higher compounding frequency when possible
- Minimize fees — even a 1% annual fee can reduce your final balance by 20-30% over decades
- Be patient — the biggest gains from compound interest come in the later years
Compound Interest vs Simple Interest
With simple interest, you only earn interest on your original principal. With compound interest, you earn interest on your principal plus all previously earned interest. Over long periods, this difference becomes enormous. On a $10,000 investment at 7% for 30 years, simple interest gives you $31,000 while compound interest gives you over $76,000.