If you have an investment earning a certain rate of interest or ROI, the rule of 72 tells you how quickly you can double your money. Just divide 72 by the interest rate or return, and that will give you the number of years. So, for example, the long-term return on investment in U.S. stocks has been 11%. If you invest today earning the same rate of return, you will double your money in 72/11 = 6.5 years.
Copyright © 2011 Mick Brooks