How do you calculate your daily calorie intake?

In general, you can use the standard Haris-Benedict calculator (which takes into account age, weight, etc.). It can be easily found online.
Here I will talk about the method of Lyle MacDonald (I personally prefer it).
*Below is a literal translation from his publications

Item 1: Basal Metabolism (Resting Calorie Expenditure)

BM - to breathe, think, move and do a bunch of other things that we don’t think about, you need to spend energy.
Calories per kilogram of body weight: for women 22, for men 24.2.

Point 2. Thermal effect of activity

TEA - this includes exercise and everything that looks like exercise. It is always fortune telling, because the value can vary from 10-20% of basal metabolism (if you sit all day), to 100% basal if you did hard physical work. If we take the average level of activity and the level of training, we get 30 - 50%. That is, 22 - 24.2 we turn into 28.6 - 33 calories per kilogram of body weight per day. This implies and includes an hour of exercise per day or so.

Item 3. Thermic effect of food

TEE - to digest the food you eat, you also need to expend energy. Of course, this can also vary a little, especially if you take extreme diets, but usually it is about 10% of the total calories. So let's add another 10%. We get 30.8 - 35.2 calories or so.

Item 4. Thermogenesis from daily activities

TPD - this includes everything except sleep, food, sports and similar activities. This is a very individual thing, it all depends on the person, and the numbers can vary greatly. It is impossible to get the exact value, so I do not take it into account at all. Also, TPD is only important in case of overeating, and I'm not sure if it should be considered in a diet setting.

In general, women or those with a slow metabolism should use a lower value (30.8 kcal/kg) and men or those with a fast metabolism should use a higher value (35.2 kcal/kg). This is in order to estimate the initial approximate value for determining the required number of calories.

The choice of fast or slow metabolism is subjective, based on previous dieting experience and past weight fluctuations. Therefore, in this case, it is simply one of the factors affecting energy consumption.
Basal metabolism can be different even in people with the same physical data, add the difference in activity here, TEE (point 3) varies a little and TPD (point 4) is just a lottery. People treat formulas like holy scriptures, although these are just approximate values.

Everything is ready, what to do next?

Then we take the obtained values ​​\u200b\u200band strictly eat on this figure based on my recommendations for BJU above. This is necessary in order to understand how we got the correct values. It is very important not to change anything, neither in diet, nor in training, nor in daily activity in order to clearly track the dynamics of weight.

If the weight is growing, then we are in an energy surplus and in order not to get fat, we need to reduce the calorie content (Maximum by 100-200 calories). If it falls, increase (Also 100-200 calories). If + - stands still, then we are lucky and we have found the basic calorie content.