Investing Duration Calculator

What actually drives your investing timeline

The calculator gives you a number. Understanding why that number is what it is helps you actually do something with it. Four inputs determine how long it takes to reach a savings or investing goal: your starting balance, how much you add regularly, the return rate you earn, and the goal itself. Every other variable is just a version of one of those four.

Contributions and return rate pull in the same direction, but they're not equal. Increasing your regular contributions has a direct, predictable effect on your timeline. Chasing a higher return rate to shorten it is riskier, since higher returns generally come with higher volatility, and volatility cuts both ways. If you can add even a small amount more each month, that tends to compress your timeline more reliably than assuming a more optimistic return. For a deeper dive into why this compounding effect matters so much, see our guide on what compound interest actually is.

Compound interest means you earn returns on your returns, not just on what you put in. In the early years this effect is modest. Over a longer timeline it becomes the dominant force, which is why starting earlier with a smaller amount often beats starting later with a larger one.

How long does it actually take? AU milestone scenarios

These worked examples start from $0, with monthly contributions and monthly compounding, using the standard compound growth formula. They're a useful sense check against whatever number your own inputs spit out.

Return assumptions are based on long-run Australian and global diversified ETF performance (think VAS, VGS, DHHF), before tax but after a typical low-cost ETF fee of 0.07 to 0.23%. 8% is a reasonable moderate assumption for a diversified AU/global mix, and 10% reflects the long-run historical average for Australian shares including dividends, so treat it as the optimistic end.

Look closely at the $1,000,000 row at 8%. It takes about 29.5 years to get there on $700 a month, but the last $500,000 of that only takes about 7.5 years, less than a third of the total time. The first $100,000 takes 8.4 years. The second $100,000 takes about 5. By the time a portfolio is nudging $500,000, it's generating tens of thousands of dollars in returns every year on its own. The early years feel slow because your contributions are carrying almost all the weight. After $100,000, returns start pulling harder. After $300,000 to $400,000, the portfolio's own growth starts to rival your monthly contribution, and that's genuinely when it gets exciting. It's also why the first $100,000 is the hardest milestone: not just psychologically, but mathematically. Push through it and the trajectory changes.

The assumptions that can wreck your timeline

The calculator is only as good as what you put into it. Four assumptions trip people up more than any others.

Ignoring inflation. The calculator works in nominal dollars, so it doesn't adjust for rising prices. The RBA targets inflation of 2 to 3% a year, and at the midpoint of 2.5%, an 8% nominal return is only about 5.5% in real terms. Over a 20 year goal at 2.5% inflation, a $1,000,000 nominal target is worth roughly $610,000 in today's money. The simplest fix is to subtract 2 to 2.5% from your expected nominal return and use that figure instead.

Unrealistic return assumptions. The ASX 200 has returned roughly 9 to 10% a year including dividends over the long run, before fees and tax. After a low-cost ETF fee of 0.07 to 0.23% and some tax drag, a realistic figure for a diversified AU and global ETF portfolio is 7 to 9% a year. If your plan only works at 15%, the fix is more contributions, not a rosier return.

Forgetting fees. Fees compound too, just in the wrong direction. Investing $500 a month at 8% for 30 years gets you to roughly $745,000. Drop that to 7.5% to reflect a fund charging 0.5% more in annual fees, and you land closer to $674,000, a $71,000 difference from what looks like a tiny percentage. Low-cost ETFs typically charge 0.07 to 0.23%, managed funds often charge 0.5 to 1.5%. Make sure the return you enter is net of fees.

Assuming perfect consistency. The calculator assumes the same contribution every month for the whole period. Real life rarely works that way. A 6 month gap in year 5 of a 20 year plan costs more than the $4,200 in missed contributions, because that money would have kept compounding for the remaining 15 years too. The real cost is closer to $13,800. A 3 to 6 month emergency fund means a rough patch in your income doesn't automatically become a gap in your investing.

Why contribution consistency beats almost everything else

Most people focus on finding a better investment or chasing a higher return. The numbers suggest that's the wrong priority. At $700 a month for 20 years, an 8% return gets you to roughly $412,000, while a 10% return gets you to roughly $532,000, a $120,000 gain. Meaningful, but look what happens if you increase the contribution instead: $700 a month at 8% for 20 years gets you $412,000, while $900 a month at 8% gets you roughly $530,000. Adding $200 a month, about $46 a week, gets you almost the same result as finding a 2% better return, and you have far more control over your contribution than you ever will over the market.

The reason consistency matters so much is that most people don't actually invest consistently. They invest when they remember, when there's extra cash lying around, when the market feels good. That's not a plan, it's a habit that breaks the moment life gets busy. The fix is automation: set up a direct debit into your brokerage the day after your pay lands, so the decision is already made before you get a chance to spend it. If you haven't nailed down what you're actually saving towards yet, our guide on setting financial goals you'll actually achieve is a good place to start before you run the numbers here.

Using this calculator for specific Australian goals

A house deposit. Australia's national median house price sits around $780,000, so a 20% deposit is about $156,000. This is a short-to-medium-term goal, so lean on a high-interest savings account return of 4.5 to 5% rather than share market assumptions. At $700 a month and 5%, that's roughly 13 years. At $1,500 a month, roughly 7 years. If your deposit is under 5 years away, keep the money out of the share market entirely.

A FIRE portfolio. The 25x annual expenses rule means a $60,000-a-year lifestyle needs a $1,500,000 portfolio. Plug that in as your target, and use a real (after-inflation) return like 7%, which is what the Australian FIRE community commonly uses for conservative long-term planning. At $700 a month and 7% real, that's roughly 35 years from $0. At $1,500 a month, closer to 23 years. Worth noting: this calculator only models money outside super, and your employer super contributions are quietly building a second pot in parallel. If FIRE is the goal, our guide to what FIRE actually means and how it plays out in Australia covers the different flavours and the bits this calculator can't see.

Your first $100k. At $700 a month and 8%, you'll have personally contributed about $71,000 of the $100,000 by the 8.4 year mark, with returns making up the rest. After that, your portfolio starts generating $7,000 to $8,000 a year on its own at 8%, which is over $600 a month in growth without you lifting a finger. Use the calculator to find the monthly contribution that gets you there in your target timeframe, then automate it.