Rule of 69(redirected from Rule of 69's)
Rule of 69
A general rule estimating how long it will take for an investment to double, assuming continuously compounding interest. One calculates this by dividing 69 by the rate of return. The rule of 69 is not exact, but it provides a quick look at the effects of compounding on an investment. It is similar to the rule of 72, which is more useful for non-continuously compounding interest.