Air-popped plain popcorn has about 30–31 calories per 1 cup popped , and roughly 387 calories per 100 grams of popped popcorn.

Quick Scoop

Popcorn is surprisingly low in calories if it’s plain and air-popped, but the number can shoot up fast once you add oil, butter, or go for movie-theater portions.

Typical calorie ranges

  • Air-popped popcorn
    • About 30–31 calories per 1 cup popped.
* About **110 calories per 1 oz (28 g)**.

* About **387 calories per 100 g**.
  • Microwave popcorn (light oil & salt)
    • Around 170 calories for ~3.5 cups popped (a common single-serve bag size).
  • Movie theater popcorn (no added butter topping)
    • Small tub : about 225 calories.
* **Large tub** : about **1,030 calories**.

Why the numbers vary so much

  • Air vs oil : Air-popped uses no added fat, so it stays low-calorie per cup.
  • Oil or butter : A couple of tablespoons of oil or buttery topping can add hundreds of calories to the same volume.
  • Serving size tricks : A “small” at the movies is often several cups; a whole large tub can go over 1,000 calories even without extra butter.
  • Weighing vs scooping : People often log “cups of popcorn” but eat out of a big bowl or bag, easily underestimating by several hundred calories.

Simple mental shortcuts

  • Think ~30 calories per cup for plain air-popped popcorn.
  • A big home movie bowl (say 8 cups air-popped) is roughly 240–250 calories if you don’t drench it in fat.
  • A “healthy”-looking microwave bag can still be 150–200+ calories once fully popped.

TL;DR:
Plain air-popped popcorn is about 30 calories per cup , but once you add oil, butter, or movie-theater portions, it can climb to several hundred or even around 1,000 calories for a big tub.

Information gathered from public forums or data available on the internet and portrayed here.