How are “Calories” on a food label calculated?

1 gram of fat = 9 calories
1 gram of carbohydrates = 4 calories
1 gram of protein = 4 calories

Note: This is what the box at the bottom of the food label means.

Here’s the math:
12 grams of fat x 9 calories per gram = 108 calories
25 grams of carbohydrates x 4 calories per gram = 100 calories
3 grams of protein x 4 calories per gram = 12 calories

108 + 100 + 12 = 220 calories