Základy investování
The power of compound interest: how small contributions grow into real wealth
Key takeaways
- Compound interest means that returns start earning further returns — the snowball effect.
- CZK 1 million over 20 years: approx. CZK 3.8 million at 7 %, approx. CZK 8.4 million at 11 %.
- Time is more important than the amount invested — starting early often leads to a higher end result.
- Fees and taxes eat into precisely this compounded portion — the most valuable part.
- Factor in inflation too: 2.5 % per year erodes roughly 40 % of purchasing power over 20 years.
Compound interest means that returns start earning returns of their own. This year you earn on your invested principal, next year you also earn on last year's return — and so it keeps "rolling up" like a snowball rolling downhill. Imperceptibly at first, then unstoppably.
A number that surprises
Invest a one-off CZK 1,000,000 and let it work for 20 years:
- at 7 % p.a. (conservative, dividend-focused portfolio) → approximately CZK 3.8 million
- at 11 % p.a. (growth portfolio, higher risk) → approximately CZK 8.4 million
A difference of just a few percentage points per year creates an enormous gap over two decades. That is the power of exponential growth — and also the reason why fund fees (TER) and taxes matter so much: they eat into precisely this compounded portion.
Time is more important than the amount you invest
The most powerful variable is not how much you put in but how long you leave it to grow. Someone who starts at 25 with smaller contributions often ends up ahead of someone who starts at 40 with larger ones. Hence the truism: the best time to start was yesterday; the second best is today.
Play around with your own numbers in the growth calculator — you will see how the result changes with the amount, monthly contribution and length of investment.
FAQ
What is compound interest in simple terms?
Reinvesting returns so that you subsequently earn on earlier returns as well. The value grows exponentially rather than linearly.
Is it worth starting with a small amount?
Yes. Over time, small regular contributions often beat later larger lump sums, thanks to the head start.
How does inflation affect the outcome?
It reduces the real purchasing power of money. At 2.5 % per year, the crown loses roughly 40 % of its value over 20 years, so always track the real, not just the nominal, result.