How Many Calories are in a Diet Pepsi?

Two women enjoy a couple diet pepsis.
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Diet Pepsi is the sugar-free alternative to the popular soft drink, Pepsi. Due to the use of the low-calorie sweetener aspartame, Diet Pepsi does not contain the high amount of sugar commonly found in other soft drinks.


Diet Pepsi is primarily composed of carbonated water, aspartame and caffeine. Potassium benzoate, phosphoric acid and citric acid give Diet Pepsi its refreshing and acidic qualities. It also contains other natural flavors and caramel color.


Calories and Fat

A 24-oz. bottle of Diet Pepsi has no fat or calories. The soft drink does not contain the ingredients that typically contribute to fat calories, such as animal products and oils. Diet Pepsi also lacks other nutrient sources that make up the total calorie count in most foods, most notably carbohydrates and protein.


Diet Pepsi is sweetened with aspartame, an amino acid compound that is between 180 and 200 times sweeter than table sugar, according to the University of Maryland Cooperative Extension. Similar to sugar, aspartame contains four calories in 1 g, but only a small amount is required to achieve the desired sweetness in the product. A 24-oz. Diet Pepsi has 354 mg of aspartame – a mere fraction of a calorie.