Nutritional breakdown of grapes

The average serving size for grapes is about one cup, or 32 grapes. As a useful measure, you can use the size of your fist to estimate the proper portion size for grapes. One cup of red or green grapes contains 104 calories, 1.09 grams of protein, 0.24 grams of fat, 1.4 grams of fiber, 4.8 milligrams ofvitaminC, 10 micrograms of vitamin A, 288 milligrams of potassium, 0.54 milligrams of iron and 3 micrograms of folate.