See how your savings or investments grow over time with compound interest. Enter principal, contributions, rate, and compounding frequency to project future value.
Compounding earns interest on both your principal and previously earned interest, accelerating growth the longer you stay invested.
Compound interest is interest calculated on both your original principal and the interest already added to the balance. Unlike simple interest, which is earned only on the principal, compounding causes your balance to grow faster over time because each period's interest itself earns interest in future periods. This snowball effect is why long-term savers and investors benefit so much from starting early — the longer money compounds, the larger the share of growth that comes from interest on interest rather than from your own contributions.
The more often interest is compounded, the more you earn, because interest is added to the balance sooner and starts earning its own interest earlier. Daily compounding produces slightly more than monthly, which produces more than annual, at the same nominal rate. The differences are modest over short periods but add up over decades. Our calculator lets you choose the compounding frequency so you can see exactly how monthly versus annual compounding changes your projected future value.
Time is the most powerful ingredient in compounding. Because growth accelerates as interest earns interest, money invested in your twenties has decades to multiply, while the same amount invested later has far fewer compounding periods. This is why a smaller sum invested early can outgrow a larger sum invested late. Even modest, consistent contributions started early often beat larger contributions started years later — a point you can demonstrate by adjusting the time horizon in the calculator.
Adding regular contributions — monthly or yearly deposits — dramatically increases your ending balance, because each new contribution also begins compounding. The calculator models this by adding your contributions to the principal each period before applying growth. You will see that consistent contributions, combined with a long time horizon, usually matter more than chasing a slightly higher interest rate.
No. The calculator assumes a constant rate of return, but real investments fluctuate year to year and savings rates can change. The projection is a useful planning estimate, not a promise. For volatile investments such as stocks, treat the figure as a long-run average outcome and remember that actual results will vary above and below the projection along the way.