Compound Growth
Returns on top of returns — the exponential math that makes time in the market the most powerful variable you control.
What You're BuyingBeginner 5 min read· Lesson 8 of 13 in Investing Fundamentals
The math
Money growing at r% per year multiplies by (1+r)^n over n years. At 10%/yr, $10,000 becomes ~$25,900 in 10 years, ~$67,000 in 20, ~$174,000 in 30 — each decade adds more dollars than the one before because growth acts on an ever-bigger base.
The two levers
Rate and TIME. Doubling your time horizon does far more than nudging your return rate, which is why starting early beats starting brilliant, and why costs (a -1% fee is a permanent -1% to r) matter so much.
Rule of 72
Years to double ≈ 72 / annual return %. At 8%, money doubles every ~9 years. Use it to sanity-check any projection instantly.