See how your money grows over time when interest compounds — and how much of the final total is pure growth.
Compound interest is interest earned on your interest. Each period, your balance grows, and the next period's interest is calculated on that larger balance — so growth accelerates over time. This calculator combines your starting amount, your regular monthly contributions, and compounding at the frequency you choose.
The bar shows the single most important insight: over a long enough timeline, the interest earned often exceeds the total amount you actually contributed. That gap is the entire reason to start investing early.
Time matters more than amount. Because compounding accelerates, the early years of contributions do the most work — they have the longest time to grow. Someone who invests for 10 years starting at 25 and then stops often ends up with more than someone who starts at 35 and contributes for 30 years straight. Starting early beats contributing more.
A quick mental shortcut: divide 72 by your interest rate to estimate how many years it takes your money to double. At 7%, money doubles roughly every 10 years (72 ÷ 7 ≈ 10.3). At 9%, every 8 years. It's a surprisingly accurate way to sanity-check compound growth without a calculator.