To calculate your daily calorie needs, you can either use an online TDEE (total daily energy expenditure) calculator or eat a specific number of calories per day for a few weeks and monitor your weight over time. Once you find a caloric intake that allows you to maintain your current weight, you can conclude these are your daily calorie needs (maintenance calories). If you want to lose weight, you will need to eat below your maintenance calories. And if you want to gain weight, you will need to eat above your maintenance calories.