Dr. Gourmet Says... The idea that popcorn does not contain calories is a myth. 100 grams of un-popped popcorn contains 375 calories, while 100 grams of popped has a similar amount at 387 calories. The difference is that 100 grams of un-popped kernels is about 1/3 cup and that will make a LOT of popped popcorn. Somewhere in the neighborhood of 13 cups.