According to the USDA National Nutrient Database, un-popped popcorn kernels contain 105 calories per ounce. Unpopped popcorn has slightly more calories than cooked popcorn kernels, according to The Popcorn Board.
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How it Works
Popcorn kernel hulls are made up of fat, protein, carbohydrates and water. When heated, pressure builds inside, the kernel expands and explodes, forming edible popcorn.
Ohio State University Extension reports that serving sizes on popcorn labels vary from 2 to 3 tbsp. of unpopped kernels per serving, which results in 4 to 7 cups of popped corn. Four cups of plain, air popped popcorn has about 124 calories.
What can be so confusing about the calories in unpopped popcorn vs. popped popcorn is that popcorn expands about 35 to 40 times the size of the kernel, according to Randy Landsberg from the Yerkes Winter Institute at the University of Chicago. So while an ounce of kernels with 105 calories may seem high, once cooked, that ounce will fit into a tub that fits 4 cups and serves two or more people.