You want to double your income. Even more so, you want to know how long it will take you to double your income. The, you will be really glad to find out that an unbreakable rule of mathematics dictates exactly how long it will take.

Here is the rule ...

Divide the annual rate of interest into the number 72 and that exactly equals how many years it will take you to double your income.

It's that simple and it is exactly accurate.

For example, let's say you earn 2% interest in a bank savings account and you have $1000 invested there. Divide 2 into 72 and you get 36. That means that your $1000 will automatically, mathematically become $2000 in exactly 36 years. Well, that may not be too exciting to you, but either is 2% interest.

So, let's say you buy a stock that offers a dividend of 4%. That same $1000 will become $2000 in 72 / 4 = 18 years. Well, 18 years is twice as good as 36 years -- because 4% is twice as good as 2%.

The chart below shows some sample annual interest rates and the number of years required to double.

1% 72 years

2% 36 years

3% 24 years

4% 18 years

5% 14.4 years

6% 12 years

7% 10.3 years

8% 9 years

9% 8 years

10% 7.2 years

11% 6.5 years

12% 6 years

18% 4 years

24% 3 years

36% 2 years

You can easily see the great advantage of getting a higher interest rate return on your money. It makes getting to double much much faster. There is another fascinating aspect to the Rule of 72 -- it does not have to be years. It can be any period of time.

For example, if you earn, say, 4% return PER MONTH, then it will take you 72 / 4 = 18 months!

And, that is the mathematical Rule of 72!