It all depends on whether you are talking about calories or Calories. When we talk about food, we should use Calories (Big C), which are actually kilocalories (1000 calories.) On the other hand, calories (Little c) are a much smaller unit used to measure energy in chemistry and physics. Ten Calories are equal to ten thousand calories. Not every source capitalizes the food Calorie, so check to be sure which unit you are using.

You can use either to calculate your diet, but be sure you stick with one choice. No fair calculating your allowed intake in calories, and then measuring your allotment of cake in Calories.