Calculating a company's percent of total annual sales for each distinct category assists in identifying sources of sales volume. If you ran a department store, you might want to know what percent of total annual sales were derived from electronics, clothing, home and garden, automotive and toys. Assuming those categories represented all categories of the store, you can calculate the total sales volume at the end of the year, and then calculate the percentage of total sales represented by each category.

Tabulate the total annual sales for each category. For example, assume you made $5 million from electronics, $4 million from clothing, $3 million from home and garden, $2 million from automotive and $1 million from toys.

Add the sales volume from each category from the previous step to calculate the total sales. In the example, the total sales volume is $15 million.

Divide each category total by the overall total and then multiply by 100. This gives you the percent of total sales represented in each category. For example, divide electronics' $5 million in sales by the $15 million overall total to get 0.3333. Multiplying this by 100 converts it to percentage format, or 33 percent. Likewise, clothing, home and garden, automotive and toys represented 26.67 percent, 20 percent, 13.3 percent and 6.7 percent, respectively.