See how your savings or investments grow over time with compound interest and regular monthly contributions.
Why compound interest is so powerful
Albert Einstein reportedly called compound interest the eighth wonder of the world. The reason is simple: your earnings generate their own earnings. Given enough time, even modest contributions can grow into a substantial sum — the growth bar in the table above shows how the curve steepens in later years.
Start early, contribute consistently
Time is the single most important factor in compounding. Someone who invests for 30 years will typically end up far ahead of someone who invests twice as much but for only 15 years. Adjust the years slider to see how much your time horizon matters.
Estimates for educational purposes only — not financial advice. Investment returns are not guaranteed and may be negative in any given period.
Frequently asked questions
What is compound interest?
Compound interest is interest earned on both your original principal and on the interest you've already accumulated. Over time this 'interest on interest' causes your balance to grow exponentially rather than linearly.
How do monthly contributions affect growth?
Regular contributions add fresh principal that also starts compounding. Small, consistent monthly deposits often end up contributing more to your final balance than the initial lump sum, especially over long horizons.
What return rate should I use?
Historically, a diversified stock market portfolio has returned roughly 7–10% per year before inflation. Savings accounts and bonds return much less. Use a rate that matches where your money is actually invested.
Does compounding frequency matter?
Yes, but modestly. More frequent compounding (monthly vs. annually) produces a slightly higher balance for the same rate. The bigger drivers of growth are your contribution amount, rate, and time horizon.