How calorie calculator works
Your total daily energy expenditure (TDEE) is the number of calories you burn in a day, combining your Basal Metabolic Rate with the energy used by activity and digestion. To lose weight you eat below TDEE; to gain weight you eat above it. A pound of body fat is roughly 3,500 calories, so a daily deficit of 500 kcal tends to lose about one pound per week.
This calculator first computes your BMR using the Mifflin-St Jeor equation, then multiplies it by an activity factor: sedentary 1.2, light 1.375, moderate 1.55, active 1.725, and very active 1.9. It then reports your maintenance calories plus targets for mild loss (-250), loss (-500), mild gain (+250), and gain (+500).
Pick the activity level that matches an average week, not your best day. Sedentary means a desk job with little exercise; moderate means 3 to 5 workouts a week. The numbers are estimates that assume steady body composition — as you lose or gain weight, recalculate. Treat them as a starting point and adjust based on real results over a few weeks.