Compound Interest Calculator
Project how an investment grows with compound interest.
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See the power of compounding on your savings. Enter your starting amount, annual interest rate, number of years and how often interest compounds, and instantly get your future value and total interest earned. It is great for planning savings and investments, and calculates privately in your browser.
Why compounding looks unremarkable and then does not
Compound interest earns returns on your returns, so growth accelerates rather than staying flat. Over a few years the difference against simple interest is small and easy to dismiss. Over twenty or thirty it becomes the dominant factor, and the majority of a long term balance ends up being growth rather than the money you put in. This is why starting earlier matters far more than contributing more later.
Frequency, contributions and the two things that dominate
How often interest compounds does change the outcome, and monthly beats annually, but the effect is modest. What actually decides the result is the rate and the time. Regular contributions are the other lever, and they behave differently from the starting amount: each one has less time to grow than the last, which is another reason early contributions carry disproportionate weight.
What a projection does not include
- Inflation. A figure thirty years out will not buy what it appears to.
- Tax on gains, which varies by country and account type.
- Fees, which compound against you exactly as returns compound for you.
- Volatility. Real returns are not a smooth annual rate, and the order of good and bad years matters.
- This is a general projection, not financial advice, and past returns do not predict future ones.
How to use Compound Interest Calculator
- 1
Enter the principal, rate and years.
- 2
Choose how often interest compounds.
- 3
Read your future value and interest earned.
Frequently asked questions
Yearly, half-yearly, quarterly, monthly and daily.