The easiest way to do this in relation to the finished product. The producer must indicate on each package shelf life and composition of the product, including vitamins, minerals and energy value - the same number of calories. Generally, the amount indicated for 100 grams. Therefore, you will need to know the weight in grams eaten portions, and then divide it by 100 and multiply by the number of calories per hundred grams.
In that case, if you buy fresh food or cook some food for yourself, count will be more difficult. In this case, you will need to table calorie foods. It can be purchased in bookstores - it is often included in various books on weight loss. Also many websites on the Internet with the same data. Example of the table you'll find on this portal - http://www.missfit.ru/diet/table-calory/.
Next, you will need to do the calculation in grams of everything you eat for a day, and then multiply each portion on a high-calorie foods and share figure for a hundred.
In this case, note that the tables more often with the weight of the dry product. Therefore, a lot of, for example, pasta, you can not count after and before cooking.
With time counting calories will you in the habit and you will not need every time to refer to tables. After all, according to calorie food products - a convenient way to weight correction. You can eat any food, just do not forget to limit themselves in their numbers.