What is the Calorie Calculator?
How many calories should you eat per day? It depends on your Basal Metabolic Rate (BMR) and how active you are. This calculator first computes your BMR with the Mifflin-St Jeor equation, then multiplies it by a scientifically established activity factor to find your Total Daily Energy Expenditure (TDEE) — your maintenance calories.
From there, the math of weight change is simple: a deficit of roughly 500 calories per day produces about 0.5 kg of fat loss per week, while a 250-500 calorie surplus supports steady, lean muscle gain when paired with strength training.
Calorie Calculator Formula & How It Works
- Sedentary (desk job): × 1.2
- Lightly active (1-3 workouts/week): × 1.375
- Moderately active (3-5 workouts/week): × 1.55
- Very active (6-7 workouts/week): × 1.725
- Extra active (physical job + training): × 1.9
Your activity factor scales resting metabolism up to real-world burn. Most people overestimate their activity level — if you sit most of the day and train 3 times a week, 'lightly active' is usually the honest choice. Weight loss target = TDEE − 500; mild loss = TDEE − 250; gain = TDEE + 250 to 500.
Worked Examples
Man, 30, 75 kg, 175 cm, moderately active
BMR ≈ 1,699. TDEE = 1,699 × 1.55 ≈ 2,633 calories to maintain. About 2,133/day loses ~0.5 kg per week; about 2,883/day supports lean gaining.
Woman, 28, 60 kg, 162 cm, lightly active
BMR ≈ 1,312. TDEE = 1,312 × 1.375 ≈ 1,804 calories to maintain; roughly 1,554/day for mild weight loss.
Expert Tips
- Track your actual weight trend for 2-3 weeks and adjust intake by 100-200 calories if the scale isn't moving as planned.
- Protein of 1.6-2.2 g per kg of body weight preserves muscle while dieting.
- Don't cut more than 25% below TDEE — aggressive deficits are hard to sustain and burn muscle.