What does starting 10 years earlier actually do?
In compound growth, time is the heaviest input — the same R1,000 a month at 10% a year is about R760,000 after 20 years, and about R2.3 million after 30.
Same contribution, same return: the extra decade does roughly two-thirds of the work.
Why the last years do the most work
Compounding is growth on growth: each year's returns start earning their own returns. That makes the curve deceptively flat at the start and steep at the end — for years it looks like nothing is happening, and then most of the outcome arrives in the final stretch.
Starting early isn't about the money the early years add. It's that the early years buy you the steep part of the curve.
The doubling lens
The rule of 72 makes it intuitive: at 10% a year, money doubles roughly every 7 years. Start at 25 instead of 35 and your money gets one extra doubling — and the final doubling is worth as much as all the previous growth combined.
What waiting costs, in rand
R1,000 a month, at an assumed 10% a year, compounded monthly:
- After 10 years — about R205,000 (R120,000 contributed)
- After 20 years — about R760,000 (R240,000 contributed)
- After 30 years — about R2.26 million (R360,000 contributed)
- After 40 years — about R6.33 million (R480,000 contributed)
Read the gaps between those lines, not the lines themselves: the third decade adds about R1.5 million; the fourth adds about R4 million. Waiting ten years doesn't delay the outcome — it deletes the biggest slice of it.
The graph they sell you — and the one you live through
Most financial institutions will sell you the exponential graph: a smooth curve sweeping up and to the right, without a single bad year on it. Reality doesn't grow like that. Real markets lurch — strong years, flat stretches, drawdowns that hand back years of gains before the climb resumes.
Here's the part the smooth graph hides: the average return can be identical while the journey feels completely different — and it's the journey that shakes people out. The investors who ended up with the big numbers weren't the ones who found smooth markets. They were the ones who stayed invested through jagged ones.
The honest caveats
- 10% is an assumption, not a promise — markets pay unevenly and sometimes negatively
- Inflation shrinks what those rand will buy: the real return is what matters for the lifestyle the money funds
- Fees compound too, in the wrong direction — a percent a year quietly claims a large slice over decades
Late isn't lost
The same arithmetic that punishes waiting rewards starting — whenever that is. Forty-five beats fifty-five by exactly the same mechanism that twenty-five beats thirty-five; the curve just pays less for less time. The one input that is genuinely gone is yesterday.
Try it with your own numbers
Set a monthly amount, an assumed annual return, and how long the money grows — then set a delay, and see the two futures side by side: start now versus start later, and what the waiting costs. An assumption machine, not a forecast. Inputs stay on your device.
Your numbers stay on your device — nothing you type here is sent or stored. This is a generic guideline calculation, not advice. For advice, speak to a vetted, FSCA-registered planner.
Terms used on this page
- compounding
- Growth on growth: returns earn their own returns. It is why time in the market matters more than the size of any single deposit.
- rule of 72
- A quick mental shortcut: divide 72 by the annual return to estimate how many years money takes to double. At 10%, roughly every 7.2 years.
- real return
- Growth after inflation — the increase in what your money can actually buy, not just the number on the statement.
Reviewed July 2026