Rule of 72 Calculator

Your details

The compound annual growth rate, e.g. 8 for 8% per year.
%
72 divides cleanly for mental math; 69.3 (ln 2 × 100) is the exact value at small rates; 70 is a common middle ground.
Turn on to see how a starting balance grows through its first few doublings.
Currency
Result
At 8% per year, your money doubles in about 9 years (exact: 9.01).
Years to double (rule)9yr
Exact years to double9.01yr
Years to triple14.3yr
Years to quadruple18yr
Double9
Triple14.3
Quadruple18

At 8%, expect to double in about 9 years.

  • The Rule of 72 gives 9 years; the exact answer is 9.01 years, a difference of 0.01 years.
  • In 18 years you would expect roughly 4x your starting amount, and 8x in 27 years.
  • This assumes the return is reinvested and compounds, with no contributions, withdrawals, taxes, or fees.

Next stepTurn on "Project a starting amount" to see the value at each doubling.

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