Compound interest calculator
See how compounding and regular contributions grow your money over time. Enter a starting amount, how much you add and how often, an expected annual return and a time frame, and the calculator shows your projected balance, how much is contributions versus interest, an interactive growth chart, and a full year-by-year breakdown you can download. AUD, no signup.
Calculator
Year-by-year breakdown
| Year | Total deposited | Interest | Balance |
|---|
Projection only, before tax and inflation. Assumes a steady annual return; real investments fluctuate. General information, not financial advice.
How compound interest works
Compound interest is interest earned on both your original money and the interest you have already earned. Because each year's interest joins the pile that earns next year's interest, the balance grows in an accelerating curve rather than a straight line. Add regular contributions on top, and every contribution starts its own compounding from the day it lands.
The calculator runs this month by month: it grows your balance at the rate implied by your chosen compounding frequency, adds your contributions, and tracks how much of the final figure is money you put in (deposited) versus money the compounding generated (interest). The gold area on the chart is that interest, and watching it overtake your contributions over time is the whole point.
Why starting early matters
The single biggest driver of a compound result is time, not the contribution size. Money invested early compounds for longer, so an early start often beats a larger amount started later. That is why the chart curves upward steeply in the final years: the interest is now large enough to generate serious interest of its own.
A common way Australians put compounding to work is a long-term, regular investing habit, the same idea behind dollar cost averaging. For those building a long-term crypto position, staking rewards can compound too. If that is your plan, start with a reputable AUSTRAC-registered exchange.
Popular Australian crypto exchanges
All three are AUSTRAC-registered Australian exchanges. Crypto is volatile; only invest what you can afford to lose.
Crypto and shares are volatile and do not grow in the smooth line shown here; only invest what you can afford to lose. Returns are never guaranteed.
Frequently asked questions
Compound interest is interest earned on both your original money and the interest already added, so it grows faster over time. The standard formula is A = P(1 + r/n)^(nt), where P is the starting amount, r the annual rate, n how many times a year it compounds, and t the number of years. When you also add regular contributions, each contribution starts earning its own compounding too. This calculator runs the full month-by-month maths for you, including your contributions and chosen compounding frequency.
Simple interest is calculated only on your original amount, so it grows in a straight line. Compound interest is calculated on your original amount plus all the interest already earned, so it grows faster and faster, in a curve. Over short periods the difference is small, but over decades it is enormous. That accelerating curve is why compound interest is often called the most powerful force in investing, and why this calculator plots it as a chart.
Adding money more often, and earlier, generally produces a larger final balance, because each contribution has more time to compound. Contributing 100 dollars a week and 433 dollars a month put in similar amounts over a year, but the weekly contributions start compounding sooner. The effect is modest over a year and more noticeable over decades. Use the frequency selector to compare weekly, fortnightly, monthly, quarterly or annual contributions.
That is a personal assumption and this tool is general information, not advice. As a rough guide, historical long-run share-market returns have often been quoted around 7 to 10 percent before inflation, cash and term deposits much lower, and volatile assets like crypto far higher but with far higher risk and no guarantee. The honest approach is to run a few scenarios, including a conservative one, rather than relying on a single optimistic number. Past returns never guarantee future results.
No, it shows the pre-tax, pre-inflation projected balance, which is the standard way these calculators work. Real returns are lower once tax on earnings and the eroding effect of inflation are considered. As a simple adjustment, you can enter a lower real rate (your expected return minus inflation) to see the result in today's dollars. For the tax treatment of investment and crypto gains in Australia, see the related tax guides.
Yes. The maths is the same for any investment that grows at a compounding rate, whether that is a savings account, shares, an index fund or a long-term crypto position. Just enter your expected annual return for that asset. Keep in mind that higher-return assets like crypto and shares are volatile and do not grow in the smooth line the chart shows; the projection is a long-run average, not a prediction of any single year.
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