Simple vs compound interest
Simple interest only ever grows on your original amount. Compound interest grows on your original amount plus all the growth you've already earned. In other words, your returns start earning their own returns. That small difference becomes enormous over time.
Imagine you invest R10,000 and it grows 10% in a year - that's R1,000, leaving you with R11,000. The next year, 10% is calculated on R11,000, not R10,000, so you earn R1,100. Each year the base gets bigger, so each year's growth gets bigger too. That snowball is compounding.
The three ingredients of compounding
- Time - the longer your money compounds, the more dramatic the effect
- Rate of return - a higher return compounds faster (but usually carries more risk)
- Consistency - adding money regularly feeds the snowball
Why starting early beats investing more
This is the part that surprises people. Because compounding rewards time, years in the market often matter more than rands invested. Someone who starts small in their twenties can end up ahead of someone who invests far more but starts in their forties - simply because their money had more time to compound.
The best time to start was years ago. The second-best time is today. With compounding, every year you wait is a year of growth you can't get back.
A simple illustration
Consider two investors, each earning an assumed 10% a year (for illustration only - real returns vary and aren't guaranteed):
| Thandi | Sipho | |
|---|---|---|
| Invests | R1,000/month from age 25 to 35, then stops | R1,000/month from age 35 to 65 |
| Years contributing | 10 years | 30 years |
| Total contributed | R120,000 | R360,000 |
| Who tends to have more at 65? | Thandi often ends up ahead - despite contributing a third as much - because her money compounded for far longer. | |
The exact figures depend on the return, but the lesson holds: an early start is hard to beat.
The rule of 72
Want a quick estimate of how long it takes money to double? Divide 72 by your annual return. At 8% a year, money roughly doubles every 9 years (72 รท 8). At 12%, about every 6 years. It's a handy mental shortcut for the power of compounding.
Compounding cuts both ways
The same maths that grows your investments also grows your debt. High-interest debt - like credit cards or store accounts - compounds against you. That's why paying off expensive debt is often one of the best "returns" you can get before investing.
How to put compounding to work
- Start now, even with a small amount - time is the ingredient you can't buy back.
- Invest regularly with a monthly debit order so you keep feeding the snowball.
- Reinvest dividends and growth rather than withdrawing them.
- Keep costs low - fees compound against you just like interest.
- Use tax-friendly accounts like a TFSA, where growth compounds tax-free.
Learn the habit with EZvest
Compounding rewards consistency, and consistency is a habit you can build. The EZvest Learning Hub turns concepts like this into short lessons and quizzes that pay you XP, while FinBot can explain any money idea in plain language - all as an educational tool, with your decisions staying yours.
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Launch EZvest - it's free to start ->Educational content only. This article is general information, not financial advice. The examples use assumed returns for illustration; real investment returns vary, are not guaranteed, and can be negative. Always consult a licensed financial professional before making decisions. How we research and review these guides.