The Rule of 72
Divide 72 by your annual return rate to estimate how many years it takes to double your money. At 7% return, your money doubles roughly every 10.3 years. At 10%, it doubles every 7.2 years.
Years to Double = 72 ÷ Annual Return Rate
Time Is the Multiplier
A $10,000 investment at 7% annual return grows to roughly $76,123 after 30 years — without adding another dollar. Add $500/month and it becomes over $600,000. The earlier you start, the less you need to save.
Model your own compound growth
Use our FIRE calculator to see how your savings grow over time with compound interest.