Compound interest calculator
What your savings grow to — after tax, fees and inflation, not just the headline.
Uses the ATO's 2026–27 resident tax rates, checked 8 November 2026. Runs in your browser — nothing you type is sent anywhere. Sources: ATO individual income tax rates.
Why this calculator shows less than the others
Most compound interest calculators assume you keep every cent of interest. In Australia, savings interest is taxed at your marginal rate each year, so less is left to compound. Over decades that gap grows. Fund fees do the same, and inflation shrinks what the final amount will buy.
The green line is what you'd actually have. The orange line is what that would buy in today's prices.
Compound interest example: what tax takes
$10,000 to start, $200 added each month, 5% a year compounded monthly, with tax taken at 30% on the interest each year. 'No tax' is what most calculators show.
| Time | You put in | No tax | After 30% tax | Lost to tax |
|---|---|---|---|---|
| 10 years | $34,000 | $47,527 | $42,870 | $4,657 |
| 20 years | $58,000 | $109,333 | $89,491 | $19,842 |
| 30 years | $82,000 | $211,129 | $155,615 | $55,514 |
Common questions
How is interest taxed in Australia?
Interest is added to your taxable income and taxed at your marginal rate, plus the 2% Medicare levy. For 2026–27 that's 0% up to $18,200, then 15%, 30%, 37% or 45%. Your bank doesn't take it out — you pay it when you lodge your tax return.
What's the compound interest formula?
A = P × (1 + r/n)^(n×t), where P is the starting amount, r the yearly rate, n how many times a year interest is added and t the number of years. Regular deposits are added on top.
Does daily or monthly compounding make much difference?
Very little. $10,000 at 5% for a year earns $511.62 compounded monthly and $512.67 compounded daily. The rate and how long you leave it matter far more.
Can I use this for super or ETFs?
Roughly. Super earnings are taxed at up to 15% inside the fund, and ETFs and managed funds charge fees and don't have fixed returns. Pick the closest tax rate and add the fee under 'Compounding, fees and inflation'.