See how a starting amount plus regular contributions grows when interest compounds. Watch how much of your final balance comes from your own money versus growth.
Compound interest is interest earned on your interest. In the first year you earn a return on your principal. In the second, you earn a return on the principal plus last year's gain. Repeat for decades and the growth accelerates — the balance curves upward rather than rising in a straight line, because each year's base is larger than the last.
The single biggest driver of a compound result is how long the money grows. Dollars invested early have the most years to snowball, which is why a modest amount started in your twenties can outgrow a larger amount started in your forties. Consistent contributions plus time do most of the work — far more than chasing a slightly higher rate or compounding frequency.
Early on, most of your balance is money you put in. But as the years pass, growth takes over — and in a long enough horizon, the majority of your final balance can come from compounding rather than contributions. The calculator above shows that split, which is the clearest way to see why patience pays.