Use conservative, mid, and optimistic return assumptions to see a realistic range of outcomes — then decide what’s feasible for your budget.
Open the Money Growth CalculatorFor Australians, $100 a week invested consistently over 30 years represents a realistic path to a half-million dollar portfolio outside of superannuation. Directed into a low-cost ETF like VAS or VGS, and assuming a 7% average annual return broadly in line with long-run ASX and global index performance, your $156,000 in contributions grows to around $529,000 — with compounding doing more than twice the work of your contributions alone. Someone starting this habit at 35 could reach retirement age with a substantial investment portfolio running alongside their super. Tools like Sharesight let you track how your actual returns compare to these projections year by year.
Thirty years is where $100 a week becomes genuinely transformative. Here's the comparison across time horizons at a 7% return:
| Time period | Total contributed | Final balance (7%) | Growth from compounding |
|---|---|---|---|
| 10 years | $52,000 | ~$75,000 | ~$23,000 |
| 20 years | $104,000 | ~$274,000 | ~$170,000 |
| 30 years | $156,000 | ~$529,000 | ~$373,000 |
Contributions triple from 10 to 30 years, but compounding growth increases more than 16 times — from $23,000 to $373,000. Starting early and staying consistent is what drives that difference.
| Return rate | Final balance | Total contributed |
|---|---|---|
| 5% (conservative) | ~$361,000 | $156,000 |
| 7% (mid) | ~$529,000 | $156,000 |
| 10% (optimistic) | ~$980,000 | $156,000 |
Investing $100 a week for 30 years means contributing $156,000 of your own money — yet at a 7% return, compounding adds a remarkable $373,000 on top, growing your balance to around $529,000. Thirty years is where $100 a week becomes genuinely life-changing — at 10% returns you're approaching a million dollars from a habit that costs less than many people spend on coffee and lunches. For someone starting at 35, this could mean retiring at 65 with half a million dollars built entirely from a modest weekly contribution.
If you invest $100/week for 30 years, the result depends heavily on the return rate. Use the calculator to test a conservative, mid, and optimistic scenario.
It’s a solid starting habit. The best amount is one you can maintain consistently, then increase over time.
Use 5% for a conservative baseline, 7% for a mid-range estimate, and 10% as an optimistic scenario.
No. Treat results as estimates. You can lower your assumed return rate to be more conservative.
For long-term modelling, converting to monthly is usually close enough.
See the simple explanation on /how-compound-interest-works.html.
Keep exploring — these pages connect directly to calculators so you can run your own numbers.