Calorie Calculator

Basal Metabolic Rate (BMR) is the number of calories your body burns at rest just to keep you alive — breathing, circulating blood, regulating temperature, and maintaining cells. This calculator uses the Mifflin–St Jeor equation, the most accurate formula recommended by the American Dietetic Association. For men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5. For women, the constant at the end is −161 instead of +5.

Total Daily Energy Expenditure (TDEE) is BMR multiplied by an activity factor that estimates calories burned through movement and exercise. The factors used here range from 1.2 (sedentary, desk job, no exercise) to 1.9 (extra active, intense daily training). TDEE is your maintenance calorie level — the intake at which your weight stays stable.

To lose or gain weight, you create a calorie deficit or surplus relative to TDEE. A daily deficit of 500 calories typically produces about half a kilogram (one pound) of weight loss per week, since one pound of fat stores roughly 3,500 calories. A 500-calorie surplus paired with strength training supports gradual lean muscle gain. Avoid extreme deficits — they slow metabolism, cause muscle loss, and are hard to sustain.

These numbers are estimates. Actual energy needs vary with body composition, genetics, hormones, sleep, stress, and the thermic effect of food. Track your weight weekly and adjust intake by 100–200 calories if results stall. For medical conditions or significant weight goals, consult a registered dietitian. Macronutrient distribution (protein, carbs, fat) and food quality also matter — calorie targets are only one piece of a healthy nutrition plan.

Activity multipliers are estimates that work for most people but have meaningful error bars. The classic five-level scale (sedentary, lightly active, moderately active, very active, extra active) is simple but can be off by 200–500 calories per day depending on your specific job, training intensity, and non-exercise activity (fidgeting, walking, standing). Wearable fitness trackers improve estimates by measuring heart rate and movement directly, though even they are imperfect.

Metabolic adaptation is a real and frustrating phenomenon. When you maintain a calorie deficit for weeks or months, your body responds by lowering BMR slightly, reducing non-exercise activity, and increasing hunger hormones. This is why weight loss often slows after the first few weeks even when intake stays constant. Diet breaks (1–2 weeks at maintenance calories every 6–8 weeks of dieting) and refeeds can mitigate this effect and improve long-term adherence.

Macronutrient distribution matters alongside total calories. Protein should typically make up 25–35% of calories during a deficit to preserve muscle mass — aim for 1.6–2.2 grams per kilogram of bodyweight. Fats should make up at least 20–25% of calories to support hormone production. Carbohydrates fill the remainder and fuel high-intensity activity. Food quality matters too: minimally processed whole foods improve satiety and nutrition density at any calorie level.

Special populations need adjusted calculations. Pregnant women generally need an additional 340 calories per day in the second trimester and 450 in the third. Nursing mothers need 450–500 extra calories. Athletes in heavy training, growing teenagers, and people recovering from illness or surgery all have elevated requirements. Older adults often need fewer calories due to reduced muscle mass and activity. When in doubt, consult a registered dietitian for personalized guidance.