Calculating how many calories to eat involves considering your Basal Metabolic Rate (BMR) and your activity level. You can start by using the Harris-Benedict equation to estimate your BMR, and then multiply it by an activity factor to find your Total Daily Energy Expenditure (TDEE). Are you trying to maintain, lose, or gain weight? Knowing your goal can help adjust your calorie intake accordingly. How do you feel about your current eating habits?