The number of calories a person should eat in a day depends on various factors, such as age, gender, height, weight, activity level, and overall health.

A general guideline for adults is to consume around 2000-2500 calories per day, but this can vary widely. For example, an active man or woman may require more calories to meet their energy needs, while a sedentary person may require fewer calories.

If you are looking to lose or gain weight, you may need to adjust your calorie intake accordingly. A calorie deficit of 500-1000 calories per day is often recommended for safe and sustainable weight loss, while a calorie surplus of 500-1000 calories per day is recommended for healthy weight gain.

It's always a good idea to consult with a healthcare professional or registered dietitian to determine the appropriate calorie intake for your individual needs and goals.