How to effectively calculate the calorie intake?

Write it down: Keeping track of your caloric intake is simple, diligent accounting. Write down every that passes your lips except water. Measure or weigh what you cook or prepare at home. There are tables available on the internet or in books to list the calories in foods. All prepared foods have calorie values listed somewhere, whether on the packaging or in the restaurant. You just have to keep good records.

Watch portion size: Agree. Remember that your portion size may not be the "official" portion size, often not. Check the single bottle of beverage, for example, doesn't contain multiple servings listed on the label. All my new patients are asked to bring a 3 day diet diary (longer than that gets pretty old for them), include at least 1 weekend day; people eat differently then. Include h2o. Good luck with your goals.