Question: how long does it take to double your money in mutual funds?
Answer: The math rule of 72 tells you how long it will take to double your money at a given rate. The interest rate times the number of years to double compounded equals 72. So to double an investment in 10 years, divide 72 by 10. A mutual fund needs an average annual return of 7.2 percent to double in 10 years.