Scoop sizes are different, so are the calories for each brand of ice cream. Plain or regular ice cream seems to be lower in calories than are ice creams that are labelled rich or have additional additives like chocolate chips, etc. Best way to know the calories is too look at the label of your choice of ice cream. It will indicated size of portion and calories.
1 cup chocolate ice cream = 260 - 377 calories
1 cup of strawberry ice cream = 222 - 230 calories
1 cup vanilla ice cream = 240 - 356 calories