Free Online Compound Interest Calculator
See how your savings grow over time with the power of compounding.
Compound interest means you earn interest on your interest. The more often interest is compounded, the faster the balance grows at the same stated annual rate.
Year-by-year growth
| Year | Balance | Contributions | Interest earned | Growth this year |
|---|
About the Compound Interest Calculator
Compound interest is interest calculated on both the original principal and the interest that has already been added to the balance. It is the reason long-term savings can grow much faster than a simple interest calculation suggests.
The compound interest formula
A = P × (1 + r / n)n × t, where A is the future value, P is the principal, r is the annual rate as a decimal, n is the number of compounding periods per year, and t is the time in years. The interest earned is A − P.
Compounding frequency matters
With a 8% annual rate, monthly compounding produces a slightly higher return than annual compounding because interest is added to the balance twelve times a year instead of once. The effective annual rate (EAR) shows the true yearly return after compounding.
Monthly contributions
Regular deposits are where compounding becomes powerful. Set a monthly contribution and choose whether it is added at the beginning or the end of each month. The calculator converts the stated annual rate into an equivalent monthly rate, adds each deposit, and compounds the running balance. The yearly table separates your contributions from the interest earned, so you can see how much of the final balance came from saving and how much came from growth.
How to use this calculator
- Enter the amount you are starting with.
- Enter the expected annual interest rate.
- Choose the number of years and how often interest compounds.
- Add an optional monthly contribution and choose the timing.
- Click Calculate growth to see the future value and yearly table.
Frequently asked questions
Is compound interest good or bad?
It works in your favour when you are saving or investing, and against you when you carry debt, because unpaid interest is added to the balance and starts earning interest too.
Does this calculator include regular contributions?
Yes. Enter a monthly contribution and choose whether it is added at the beginning or end of each month. The results show total contributions separately from interest earned.
Are the results guaranteed?
No. The calculator assumes a fixed rate for the whole period. Real investments and savings accounts can change rates or lose value.