I always use the rule of 72. What return you get on your investment divide it into 72 and that's how many years it will take to double your money compounding your interest. Eg if you get 10 % return. 72 / 10 is 7. 2 years. If you get 1.7 % return, 72 divided by 1.7 equals 42 years. With a 15% return you will double your 500,00 every 4.8 years. That's just basic no other factors taken into account.
