A rule stating that in order to find the number of years required to double your money at a given interest rate, you divide the compound return into 72. The result is the approximate number of years that it will take for your investment to double.
For example, if you want to know how long it will take to double your money at 12% interest, divide 12 into 72 and you get six years.
You can also run it backwards: if you want to double your money in six years, just divide 6 into 72 to find that it will require an interest rate of about 12 percent.
