If you believe the conventional wisdom that you gain weight because you eat more than you expend, of course you'll believe that “calories count” and that counting them (and minimizing them) is the only way to lose weight.
The labels on the food packets will usually tell you how many calories are contained in 100 grams or 100 millilitres of the food or drink, so you can compare the calorie content of different products. Many labels will also state the number of calories in "one portion" of the food. But remember that the manufacturer's idea of "one portion" may not be the same as yours, so there could be more calories in the portion you serve yourself!
The Talko recently demonstrated the idea by comparing a junk food to its caloric equivalent of healthy food. It shows a genious break down of our favorite foodies according to their caloric intake.
you may calculate your calorie intake using a calorie calculator