When people invest money, they care about what return they will receive, either in the short or long term. Over the course of a year, most investments' returns will vary from month to month. For the investor to see how he did over a year, he might look at his average monthly return for the year. This gives him a sense of how his investment performed during this particular period.
Determine the total return over the course of the year. For example, if you purchased a stick on January 1 for $150, and sold it on December 31 for $168, your total return for the year is $18. Your percentage return is 12 percent ( [$18/$150]*100).
To determine the average monthly return, divide the dollar return by the number of months in the period. In this case, divide $18 by 12 months to get $1.50 per month.
Follow the same approach to determine the average monthly percentage return: 12 percent divided by 12 months equals 1 percent per month.