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Compound Interest Calculator
Compound interest is the eighth wonder of the world. He who understands it, earns it. He who does not, pays it.
Attributed to Albert Einstein
The eighth wonder of the world. See how regular contributions and compounding returns snowball into serious wealth over time.
Compound interest rewards patience. The longer your money stays invested, the more each year's returns build on the last. Add regular contributions and the effect accelerates dramatically. This calculator shows both the final balance and the year-by-year growth so you can see the snowball in motion.
Educational illustration only. Returns are not guaranteed.
Investment Growth Calculator
See how your money grows with compound interest over time
Your Result
Final Balance
$20,097
You Contributed
$10,000
Interest Earned
$10,097
Rule of 72: Money doubles in
10.3 years
at 7% return
Why Compound Interest Is So Powerful
Three forces work together: time, contributions, and reinvestment. Remove any one of them and the outcome changes dramatically.
Time
The longer money stays invested, the more compounding cycles it goes through. Doubling your time horizon roughly quadruples the outcome at a fixed rate. Starting early beats starting large.
Regular contributions
Each new deposit starts its own compounding journey. Consistent monthly additions often matter more than a single lump sum, because they keep deploying capital throughout the entire period.
Reinvestment
Compounding only works if returns are reinvested rather than withdrawn. Each cycle adds to the principal, so the next cycle earns returns on a larger base. This is where the snowball effect comes from.
The Rule of 72
A quick mental check: divide 72 by your annual return rate to estimate how many years it takes to double your money. At 7% per year, your money doubles roughly every 10 years. At 10% per year, every 7.2 years. The calculator shows the exact path, but the Rule of 72 gives you a fast sanity check.
This calculator is for educational purposes only. Investment returns are not guaranteed. Past performance does not indicate future results. Results are illustrative and do not constitute financial advice. Always consult a licensed financial adviser for advice specific to your situation.
Want to model your tax situation?
See how CGT and salary sacrifice affect your real wealth outcome.