One small strawberry, which is about 7 grams in weight, is only around 2 calories. This is the type of berry you would want to put into a smoothie or on cereal. A medium strawberry, which is roughly 12 grams, has 4 calories. This is the type you would generally see eaten as a snack or placed in a pie or cake. A large strawberry or one that is 18 grams nets 6 calories.