1. Key points

  • Time matters: starting earlier usually beats saving larger amounts later.
  • The same math works against you on debt with compounding interest.
  • Investments are not guaranteed and can lose value; savings accounts at insured banks are protected up to FDIC limits.
  • The SEC's Investor.gov has a free compound interest calculator.

2. Rule of 72

Dividing 72 by an annual return rate gives a rough estimate of how many years it takes money to double. It's an approximation, not a promise.