One cup of popped popcorn weighs 2.24 ounces, according to Aqua-Calc.com. Popped popcorn weighs less than unpopped popcorn as moisture in each kernel is released during the popping process.
The Popcorn Board reports that air-popped popcorn contains 31 calories per cup, while oil-popped popcorn contains 55 calories per cup. The average American consumes 51 quarts of the snack per year. Popcorn is different from other forms of corn and maize in that its kernels have thicker hulls. These hulls allow pressure from heat, whether it is from a microwave or stove-top, to build to a sufficient degree to eventually burst or pop.