The number of calories in whey protein powder can vary depending on the brand and formulation. On average, whey protein powder typically contains around 110-140 calories per serving. The calorie content of whey protein powder can be even lower in some brands, with some products containing as few as 60 calories per serving. Factors such as added sweeteners, flavors, and other ingredients can affect the calorie content of whey protein powder. It's best to check the specific product label for the exact calorie content.