Why starting at 18 beats starting at 35: compound growth, explained simply
The same $100 a month can grow into very different amounts depending on when you start. Here is why time matters so much.
Compound growth is often called the most powerful idea in personal finance. It is also one of the simplest to explain to a teenager.
The idea in one sentence
Your money earns money, and then that money earns money too.
A simple example
Imagine saving $100 a month and investing it.
- In the first year, you put in $1,200 and it earns a little growth.
- In the second year, you earn growth on your savings and on last year’s growth.
- Every year after that, the snowball gets bigger and rolls faster.
On our home page, our calculator shows what happens when someone invests $100 a month from age 18 versus age 35, using a hypothetical return. Starting 17 years earlier adds only about $20,000 in extra savings, but because growth keeps building on itself, the final difference is many times larger.
Why young people have the advantage
Most adults can save more each month than a teenager can. What adults cannot get back is time. A young person who builds the habit early gives compound growth decades to work.
What it does not mean
Compound growth is not a promise. Real investment returns go up and down, and some years are negative. That is why we teach it together with budgeting, saving, risk and patience, so young people understand both the power and the limits.
Try it yourself: use the “Try your own numbers” calculator on our home page to change the monthly amount, starting age and return.
Investing and long-term thinking are part of our Money for Real Life program for high school students aged 14 to 17.
This article is for education only and is not financial advice.
Finansavi provides financial education, not financial advice. Examples are for learning only.