A "serving" is the amount of food recommended in consumer education materials such as MyPlate. A "portion" is the amount of a food you choose to eat at any one time — which may be more or less than a serving.

Here are some everyday comparisons to help you figure out your serving sizes.

• 1 teaspoon of margarine is the size of one dice
• 3 ounces of meat is the size of a deck of cards
• 1 cup of pasta is the size of a baseball
• 1½ ounces of cheese is the size of four stacked dice
• ½ cup of fresh fruit is the size of a tennis ball

http://www.eatright.org/resource/food/nutrition/nutrition-facts-and-food-labels/serving-size-vs-portion-size-is-there-a-difference