Compound Interest Calculator

Compound interest is interest paid on your interest. Put $10,000 away at 5% a year, compounded monthly, and it grows to $16,470 in 10 years without a single extra deposit. This tool shows that growth for any amount, rate and time frame.

Enter a starting sum, a yearly rate, the number of years and how often interest is added: daily, monthly, quarterly, twice a year or once a year. You can also add a fixed deposit at the end of each month. The result shows the final balance, the total you paid in and the part that came from interest. A chart tracks both lines year by year, so you can see the gap between them widen.

Time does most of the work. At 8%, $10,000 roughly doubles in 9 years and doubles again in the next 9. The table below shows how far apart the rates drift over 30 years. That is why starting early matters more than finding a slightly better rate. The Rule of 72 gives a quick check: divide 72 by the rate to get the years it takes to double.

The same math runs in reverse on debt. A credit card balance at 20% grows just as fast as a good investment, only against you. To see the cost of borrowing, try the Loan and EMI Calculator. For a long-term savings plan with an employer match, use the Retirement Savings Calculator. Keep in mind that the rate you enter is fixed for the whole period. Real investment returns go up and down, and fees and taxes reduce them. Treat the result as a projection, not a promise.