The Rule of 72
Do you know the Rule of 72?. It’s an easy way to calculate just how long it’s going to take for your money to double.
Just take the number 72 and divide it by the interest rate you hope to earn. That number gives you the approximate number of years it will take for your investment to double.
As you can see, a one-time contribution of $10,000 doubles six more times at a 12 percent return than at 3 percent.