The Rule of 72

The Rule of 72 is a simple way to estimate the number of years required to double an investment at a fixed annual rate of return. By dividing 72 by the annual interest rate, you get an approximate number of years it will take for the initial investment to double.

Formula:
Years to Double = 72 / Interest Rate

Examples:

1. Example 1: 6% Interest Rate
   If you invest money at an annual interest rate of 6%, the time it takes to double your investment is:
   Years = 72 / 6 = 12 years
   So, at 6% interest, your money will double in approximately 12 years.
2. Example 2: 8% Interest Rate
   At an annual interest rate of 8%, the time to double your investment is:
   Years = 72 / 8 = 9 years
   Thus, your investment will double in about 9 years.
3. Example 3: 4% Interest Rate
   For an investment with a 4% annual return:
   Years = 72 / 4 = 18 years
   It will take roughly 18 years to double your money.

The Rule of 72 is a quick calculation that works best for interest rates between 5% and 12%. It provides a useful approximation but may not be perfectly accurate for very high or very low rates.