The eighth wonder of the world: watch how small regular contributions grow into a fortune over decades.
Compound interest is the force that turns small, regular savings into life-changing wealth over time. This free calculator shows exactly how your money grows when interest earns interest — year after year. Whether you're investing in a 401(k), IRA, or brokerage account, understanding the power of compounding will keep you motivated to start early and contribute consistently. Time in the market beats timing the market.
Einstein called it the "eighth wonder of the world." The longer you let money grow, the faster it accelerates — because your interest starts earning interest. The last 10 years of a 30-year plan often produce more growth than the first 20 combined.
Someone who invests $200/month from age 25 to 35 (10 years) ends up with more at 65 than someone who invests $200/month from 35 to 65 (30 years). Time beats amount.
Chasing the hot stock or crypto of the month usually backfires. Consistent contributions to low-cost index funds over decades beat market timing.
The S&P 500 has averaged about 10% annually over the last 100 years (before inflation). Use 7% as a conservative long-term estimate for a balanced portfolio.
Yes — on debt. Credit card interest compounds the same way, which is why carrying a balance is so expensive. Paying off high-interest debt is the highest-return investment you can make.
Mathematically, immediately — but visually, around year 15–20. The curve stays flat at first, then curves up sharply. Most people quit too early and miss the payoff.