When you have a trading portfolio, you need a way to measure the performance of your investments. The total return of your portfolio measures the raw gain or loss, including any dividends that you earn. You need to include dividends because a stock may only have a nominal gain, or even a loss, but that can be offset if the company pays significant dividends. You can calculate the total return as a numerical gain or loss, or as a percentage.

Subtract the initial investment from the ending investment value of your trading portfolio to find your gain or loss. For example, if you started with $11,800 and ended with $12,300, you have a gain of $500.

Add the dividends received from your trading investment portfolio to your gain or loss to find the total return. In this example, if you received $80 in dividends, add $80 to $500 to get a total return of $580.

Divide the total return by the initial investment amount to calculate the total return on your trading portfolio. In this example, divide $580 by $11,900 to find the total return equals 0.0487, or about 4.87 percent.