Figuring the annual gain or loss on your stock portfolio helps you evaluate your investment choices for the year, as well as deciding how to position yourself better for the coming year. Measuring the gain or loss as a percentage allows you to compare investments of varying sizes. For example, a gain of $1,000 sounds good, but if you had to invest $100,000 to get it, it's not so great anymore. To figure the gain or loss, you just need to know the value of the stock at the start and end of the year in question.
Subtract the stock value at the start of the year from the stock value at the end of the year to find the raw gain or loss. For example, suppose your shares were worth $8,000 and now they're worth $9,000. You have a $1,000 gain. Alternatively, if the stock went down to $7,500, you have a loss of $500.Step 2
Divide the rate gain or loss by the value at the start of the year to figure the annual rate of growth. In this example, divide $1,000 by $8,000 to get 0.125. Alternatively, divide negative $500 by $8,000 to get negative 0.0625.Step 3
Multiply the rate of growth by 100 to find the annual stock market percentage gain or loss. Finishing the first example, multiply the rate of 0.125 by 100 to get a gain of 12.5 percent for the year. Finishing the second example, multiply negative 0.0625 by 100 to find you have a loss of 6.25 percent for the year.
Based in the Kansas City area, Mike specializes in personal finance and business topics. He has been writing since 2009 and has been published by "Quicken," "TurboTax," and "The Motley Fool."