Run 3 return-rate scenarios to see a realistic range of outcomes — then adjust your monthly amount until it fits your budget.
Open the Money Growth Calculator| Return rate | Final balance | Total contributed |
|---|---|---|
| 5% (conservative) | ~$83,000 | $36,000 |
| 7% (mid) | ~$122,000 | $36,000 |
| 10% (optimistic) | ~$226,000 | $36,000 |
Investing $100 a month for 30 years means contributing just $36,000 of your own money — yet at a 7% return, compounding adds an extraordinary $86,000 on top, growing your balance to around $122,000. Thirty years transforms a tiny monthly habit into a six-figure sum, with compounding adding more than twice what you contributed yourself. This is one of the most compelling examples of why starting early matters — $100 a month from age 30 could mean $122,000 by retirement at 60 with almost no effort.
For Australians, $100 a month over 30 years is one of the most powerful examples of what consistency and time can achieve. 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 $36,000 in contributions grows to around $122,000 — with compounding adding more than twice what you contributed. Someone starting at age 30 could have a six-figure investment portfolio by retirement from just $25 a week. It's a compelling case for starting early, even with a small amount. Tools like Sharesight make it easy to track your actual returns against these projections over the long haul.
Thirty years is where $100 a month transforms from modest to meaningful. Here's the comparison at a 7% return:
| Time period | Total contributed | Final balance (7%) | Growth from compounding |
|---|---|---|---|
| 10 years | $12,000 | ~$17,000 | ~$5,000 |
| 20 years | $24,000 | ~$52,000 | ~$28,000 |
| 30 years | $36,000 | ~$122,000 | ~$86,000 |
Contributions triple from 10 to 30 years, but compounding growth jumps from $5,000 to $86,000. Starting early with even a small amount makes an enormous difference over time.
If $100/month feels hard right now, test a smaller starting amount and increase it each year. Even small step-ups can move the result a lot over long horizons.
It can be. The biggest drivers are consistency and time. Use the calculator to compare multiple return scenarios.
Try 5% (conservative), 7% (mid), and 10% (optimistic) to see a range.
No. Treat results as estimates. You can lower your assumed return rate to be conservative.
If you can’t do both, extra time often helps a lot. Then increase contributions over time.
See /how-compound-interest-works.html.