The percentage of monthly growth expresses the change during a month in relation to the beginning amount. You may want to find the monthly growth percentage to quantify the growth of an investment or an increase in membership at a club or organization. Knowing the monthly growth rate can help you project growth rates for longer periods, such as the annual growth rate. However, especially with volatile investments, just because it increases one month does not mean it will maintain the same growth rate indefinitely.
Subtract the amount you have at the beginning of the month from the amount you had at the end of the month to find the growth. For example, if a stock you own was worth $40 at the start of the month and is worth $41 at the end of the month, subtract $40 from $41 to get $1.
Divide the growth by the beginning of the month value to find the rate of growth. For this example, divide $1 by $40 to get 0.025.
Multiply the rate of growth by 100 to convert to a percentage. In this example, multiply 100 by 0.025 to find the monthly growth rate equals 2.5 percent.
Multiply the monthly growth rate by 12 to convert to an annual rate. For example, if the monthly growth rate equals 0.5 percent, multiply 0.5 by 12 to find an annual rate of 6 percent.