The rule of 72 is a very simple way to estimate and determine the number of years required to double your investments given a fixed annual rate of interest. It can also estimate and then calculate the annual interest rate required to double an investment in a given number of years. In the rule of 72, you can either choose to calculate the annual interest rate or the number of years.
Use this formula to calculate the rule of 72
Rule of 72 ≈ 72 ÷ interest rate ≈ number of years to double