Compound Interest — The Most Powerful Force in Finance

What if you could invest less money for less time and end up richer than someone who invests more money for more time? It sounds impossible, but it's not a trick. It is the single most powerful concept in finance, and understanding it now gives you an advantage you can never get back: time.

The concept is called compound interest. It’s interest you earn not just on your original money, but also on the interest that money has already earned. It creates a snowball effect that grows faster and faster over time.Here is the most important financial example you will ever see:Person A invests 100 units of currency per month starting at age 18. They stop at age 28. Total invested: 12,000 over 10 years.Person B invests 100 units of currency per month starting at age 28. They continue until age 65. Total invested: 44,400 over 37 years.Assuming both earn a 7% annual return, at age 65, Person A has approximately 256,000. Person B has approximately 199,000. Person A invested less money for fewer years but ended up with more. Why? Because their money had an extra 10 years to grow. Time is...

Camila, 18, and her cousin, 28, both commit to investing 100 units of their currency each month. Curious, Camila opens an online compound interest calculator. She plugs in her numbers, setting the end date to age 65. Then she does the same for her cousin, starting ten years later. The results are shocking. Even though her cousin will invest over 32,000 more in total, Camila's final balance is projected to be nearly 57,000 higher. She shows him the screen. He looks at the two numbers, shakes his head, and says, "I wish I'd started at your age."