The Rule of 72 and Compounding Frequency: Why Contribution Timing Matters

Mental Math Check Before Detailed Modeling

Dividing 72 by an expected annual return percentage gives a fast approximation of how many years an untouched lump sum needs to double. For example, at 8% annualized return, doubling takes roughly 9 years.

Exact Modeling With Regular Deposits

Pair that rule-of-thumb check with our Compound Interest Calculator or explore VOO ETF Growth Projections to inspect contribution curves year by year.