In an ideal world, everyone would know exactly daily calories requirements. Each body cell would get exactly enough energy and nutrients for use.
Practically, this is impossible. Physical activity, digestion, exercise, weather conditions, stress, psychology and many other factors change calorie requirements. Most of us end up eating more than needed, due to easy and cheap availability of high caloric food.
A paying strategy is to eat 10 to 15% less than you need. Based on your weight, daily physical activity, many online tools and applications will advise a daily calorie intake to maintain your weight. Subtract 10 to 15% from the figure shown.