what is the difference between the rule of 70 and the rules of 69 and 72 
the rule of 72 or the rule of 69 may also be used the function is the same as the rule of 70 but uses 72 or 69 respectively in place of 70 in the calculations the rule of 69 is often considered more accurate when addressing continuous compounding processes and 72 may be more accurate for less frequent compounding intervals the bottom linethe rule of 70 is a calculation that provides an estimate based on a constant growth rate of how many years it takes for an investment to double in value investors may use this calculation to evaluate the investment returns of mutual funds and retirement portfolios 