Compound Interest Calculator Australia
Estimate how compound interest can grow your savings or investments over time. Test a starting balance, return rate, and regular contributions to see the long-term effect of interest on interest.
| Year | Balance | Interest |
|---|---|---|
| Yr 1 | $13,201 | +$801 |
| Yr 2 | $16,634 | +$1,033 |
| Yr 3 | $20,315 | +$1,281 |
| Yr 4 | $24,262 | +$1,547 |
| Yr 5 | $28,495 | +$1,832 |
| Yr 6 | $33,033 | +$2,138 |
| Yr 7 | $37,900 | +$2,466 |
| Yr 8 | $43,118 | +$2,818 |
| Yr 9 | $48,714 | +$3,196 |
| Yr 10 | $54,714 | +$3,600 |
How compound interest works
With simple interest, you earn returns only on your original investment. With compound interest, every period's earnings get added to your balance — and the next period you earn returns on that larger amount. The effect is slow at first, then dramatically accelerates.
A $10,000 investment at 7% p.a. for 30 years:
The Rule of 72
Divide 72 by your annual return rate to estimate how many years it takes to double your money. At 7% p.a., your money doubles roughly every 10 years (72 ÷ 7 = 10.3). At 10%, every 7.2 years. This rule works because of the exponential nature of compounding.
Why regular contributions matter so much
Adding even a small regular contribution dramatically changes the outcome. Compare starting with $10,000 at 7% p.a. for 20 years:
| Monthly contribution | Final balance | Interest earned |
|---|---|---|
| $0/month | $38,697 | $28,697 |
| $100/month | $64,568 | $40,568 |
| $200/month | $90,440 | $52,440 |
| $500/month | $167,900 | $87,900 |
Frequently asked questions
Sources
- ASIC MoneysmartAustralian Securities and Investments Commission · Consumer guidance on saving, investing, and long-term money decisions.
How this calculation works
This calculator applies the standard compound interest formula to a starting balance, an annual return assumption, and any regular contributions you add.
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Methodology
- Start with an opening balance and annual return rate.
- Apply the return assumption across the selected time horizon.
- Add regular contributions at the chosen frequency where supported.
- Show the resulting future value and year-by-year growth path.
Assumptions
- Return assumptions are illustrative and not guaranteed.
- The model does not account for tax, fees, or inflation unless the page says otherwise.
- Regular contributions are assumed to happen consistently over time.
Limitations
- Real-world investment returns vary year to year.
- After-tax returns can be materially lower than headline compound growth.
Life Calculators provides independent modelling tools based on publicly available data and standard formulas. Results are estimates only and are not financial advice.
Last updated: 17 March 2026
Compound interest guide and examples
| Year | Balance | Interest |
|---|---|---|
| Yr 1 | $13,201 | +$801 |
| Yr 2 | $16,634 | +$1,033 |
| Yr 3 | $20,315 | +$1,281 |
| Yr 4 | $24,262 | +$1,547 |
| Yr 5 | $28,495 | +$1,832 |
| Yr 6 | $33,033 | +$2,138 |
| Yr 7 | $37,900 | +$2,466 |
| Yr 8 | $43,118 | +$2,818 |
| Yr 9 | $48,714 | +$3,196 |
| Yr 10 | $54,714 | +$3,600 |