How Many Calories Should You Eat Per Day? The Science-Based Answer
The answer depends on your size, activity level, and goal. Here is how to find your exact number.
The average adult needs 1,800-2,400 calories per day to maintain weight. But averages are useless for individuals. Your number depends on your Basal Metabolic Rate (the calories burned at rest) multiplied by your activity level. A sedentary 140-pound woman needs about 1,700 calories. An active 200-pound man needs about 3,000. The range is enormous.
Finding Your Number
Step 1: Calculate BMR using the Mifflin-St Jeor equation. For men: (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5. For women: same formula minus 161. Step 2: Multiply by activity factor — sedentary (1.2), lightly active (1.375), moderately active (1.55), very active (1.725). The result is your TDEE — eat this amount to maintain weight.
Adjusting for Goals
Fat loss: subtract 500 calories from TDEE (lose ~1 lb/week). Muscle gain: add 250-500 calories. Never eat below your BMR — this is the minimum your organs need to function. A moderate 500-calorie deficit is sustainable and preserves muscle. Crash diets below BMR cause muscle loss, metabolic adaptation, and almost always lead to regaining the weight plus more.