- What interest rate should I use for Australia?
- It depends on the investment. High-interest savings accounts track the RBA cash rate; check Canstar or RateCity for current rates as they change with each RBA decision. Term deposits sit in a similar range for 1–2 year terms. The ASX 200 has returned approximately 9–10% p.a. total (dividends plus capital growth) over the long run, though with significant year-to-year volatility. Balanced super funds typically return 6.5–7.5% after fees and tax over the long term. Use 7% as a conservative base for a long-term diversified equity portfolio.
- Does compounding frequency really make a significant difference?
- On a savings account, the difference between daily and monthly compounding is small - well under 0.02% of the balance per year at typical rates. On $500,000, that is only around $50 a year, a minor effect next to the interest rate itself. For equity investments, formal compounding frequency matters less because returns are driven by market movements, not a stated rate, though reinvesting dividends (DRIP) creates a similar compounding effect. The biggest variable is always the annual return rate, not the compounding frequency.
- How much do I need to save per month to reach a target amount?
- Work backwards from your goal. To reach $500,000 in 20 years at 7% p.a. (compounded monthly) starting from $0, you need roughly $960 per month. Starting with $50,000 reduces that to about $570 per month, showing how an upfront lump sum reduces the ongoing contribution needed. Use this calculator by adjusting the monthly contribution until the final balance reaches your target. For a more targeted approach, try the Savings Goal Calculator.
- Which Australian accounts actually compound interest?
- Most high-interest savings accounts calculate interest daily but credit it monthly, so the balance compounds monthly in practice, even though no interest is lost between calculation and crediting. Term deposits typically pay interest at maturity or annually, making them effectively simple interest for a given term. ETFs do not pay a stated interest rate, but price growth and dividend reinvestment create compounding returns over time. Super fund earnings compound within a concessional 15% tax environment during accumulation.
- How does compound interest compare to simple interest?
- $10,000 at 7% p.a. for 20 years: with simple interest you earn 7% × $10,000 × 20 = $14,000, ending with $24,000. With compound interest (annual), the same investment grows to $38,697 - $14,697 more. At 30 years, compounding produces $76,123 versus $31,000 simple, a $45,123 difference on the same original $10,000. The longer the time horizon, the more dramatic the compounding advantage.
- When does compound interest really start to accelerate?
- Compound growth follows a hockey-stick curve: slow in the early years, then sharply accelerating. On a $10,000 investment at 7% compounded annually, the first decade adds $9,672 in interest, the second decade adds $19,025 (nearly double), and the third adds $37,426 (nearly double again) - each decade compounds on a balance that is itself 1.07¹⁰ times larger than the one before. The last five years of a 30-year investment can generate more growth than the first 15 years combined.
- How does compound growth work in superannuation?
- Super is one of Australia's most powerful compounding vehicles because of its low tax environment: concessional (before-tax) contributions are taxed at 15% on entry, generally well below your marginal rate, and earnings inside super are taxed at 15% during accumulation and 0% in pension phase. A 25-year-old contributing $500/month for 40 years at 7% p.a. accumulates approximately $1.3M inside super. The same gross return held outside super produces a materially smaller balance because investment earnings face marginal tax rates rather than the concessional super rate. Over four decades, that difference compounds substantially. Contribution caps apply; see the Superannuation Calculator for a fuller projection.
- Is the interest I earn in a savings account taxable in Australia?
- Yes. Interest earned in Australian savings accounts and term deposits is taxable income and must be declared on your annual tax return. It is taxed at your marginal rate - there is no 50% CGT discount, as that applies only to capital gains on assets held over 12 months. Banks report interest paid to the ATO, so it is usually pre-filled in your myTax return. If your HISA pays 5% and your marginal rate is 32% (30% income tax + 2% Medicare levy), your effective after-tax return is approximately 3.4%. This is why the tax efficiency of super, where earnings are taxed at just 15%, makes it increasingly valuable for long-term savings.