Originally Posted by basharp1

The Rule of 72:
Question, How fast can I double my money?

Answer, If I'm earning net 12% (example) annually when will it double"

Rule of 72; 72/12=6 years, $10,000 will double if you continue to earn a net of 12% annually on your investment. The graph your using above, I believe is not representative of the "rule of 72" because its based on constant net return, I.E. 12% or what ever the rate of return is. Over an extended period you could establish a mean average and calulate it from there I suppose

Originally Posted by mulp

Here's the rule of thumb: doubling time is 70 divided by rate in percent: 70/4 => doubling time of 17.5 years. For prices to double in 7 years, inflation needs to be 70/7 => 10%. (The precise numbers are 17.67 years and 10.4% respectively.)