See how your money grows with the power of compounding and regular contributions
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest, which only earns interest on the original deposit, compound interest creates a snowball effect — the longer you invest, the faster your money grows.
Albert Einstein is often credited with calling compound interest the eighth wonder of the world, and for good reason. A single lump-sum investment left to compound for decades can grow to multiples of its original value without any additional contributions.
The frequency at which interest is compounded makes a measurable difference to your final balance. Monthly compounding produces a slightly higher return than quarterly, which is better than annual compounding at the same stated interest rate. This is because more frequent compounding means interest starts earning interest sooner.
Pro tip: When comparing savings accounts or investment products, always look at the Annual Percentage Yield (APY) rather than just the stated interest rate. The APY accounts for compounding frequency and gives you a true like-for-like comparison.
Time is the most powerful variable in compound interest. Investing $200 per month starting at age 25 at 8% annual return produces dramatically more wealth by retirement than starting the same contributions at age 35 — despite only a 10-year difference in start time.
Our calculator lets you experiment with different start amounts, monthly contributions, and time horizons so you can see the impact of starting early versus waiting. Even small amounts invested consistently over long periods can produce significant wealth through the power of compounding.
The future value result shows what your investment will grow to over the period you specified. The growth multiple tells you how many times larger your investment becomes — a multiple of 5x means your money grew to five times what you put in. Use this to set realistic expectations and motivate consistent saving habits.
Compound interest is interest calculated on both your original principal and the interest already accumulated. This creates exponential growth over time — often called the snowball effect — where your money grows faster the longer it is invested.
More frequent compounding produces slightly higher returns. Monthly compounding earns more than quarterly, which earns more than annual compounding at the same stated rate. The difference increases over longer time periods and larger balances.
For long-term stock market investments, historical averages suggest 7–10% annually. For savings accounts or bonds, 3–5% may be more appropriate. Always use a conservative estimate — it is better to exceed your goal than to fall short.
Three factors drive compound growth: the amount invested (larger principal compounds more), the return rate, and above all, time. Starting as early as possible — even with small amounts — has a disproportionate impact because of the exponential nature of compounding.