The “rule of 72″ is a quick and simple way to figure out approximately how long it will take for an investment to double. You just divide 72 by how much interest you earn on an investment per year – that’s it. So if you put $100 into an account that pays 6% interest, it’ll take 12 years for your principal to double to $200 (72÷6=12).

Tags: double, interest, rule of 72