Compound Interest Calculator
Calculate how your savings or investments grow over time. Enter a principal, rate, compounding frequency, and optional contributions to see your final balance and a year-by-year breakdown.
Year-by-Year Growth
| Year | Starting Balance | Contributions | Interest Earned | Ending Balance |
|---|
Enter your investment details above to see how your money grows over time.
For estimation purposes only. Does not account for taxes, fees, or inflation.
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Frequently Asked Questions
What is compound interest?
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods — interest earning interest. Over time this creates exponential growth, which is why starting to save early makes such a large difference.
What does compounding frequency mean?
How often interest is calculated and added to the balance. Daily compounding earns slightly more than monthly or annual compounding at the same nominal rate, because each interest addition becomes part of the base for the next calculation sooner.
What is the Rule of 72?
Divide 72 by your annual interest rate to estimate how many years it takes for an investment to double. For example, at 6% per year your money doubles in approximately 72 ÷ 6 = 12 years.
How do regular contributions affect growth?
Regular contributions significantly increase the final balance because each deposit also compounds over its remaining time horizon. Even small monthly contributions added consistently can dramatically outpace a larger one-time deposit.