Understanding and using your calorie needs
BMR, PAL factor and individual differences
Your daily calorie needs are the amount of energy your body requires to maintain all its functions and support your physical activity. They consist of two components: your basal metabolic rate (BMR) and the activity expenditure caused by physical movement. Our calculator uses the Mifflin-St Jeor equation, developed in 1990, which is today regarded as the scientific gold standard for estimating basal metabolic rate.
The PAL factor (Physical Activity Level) multiplies your BMR by an activity multiplier. Someone with an office job who does little to no sport falls around PAL 1.2. Someone who trains three times a week is around PAL 1.55. Competitive athletes or people with physically demanding jobs can reach PAL values of 1.9 or higher. Choosing the right PAL factor has a considerable effect on the result: between PAL 1.2 and 1.9, the calculated total energy expenditure can differ by 400–800 kcal.
For weight loss, current nutritional medicine recommends a moderate calorie deficit of 300–500 kcal per day. This corresponds to a theoretical weight loss of about 0.3–0.5 kg per week, which is considered sustainable and healthy. Larger deficits speed up short-term weight loss but increase the risk of muscle loss, nutrient deficiencies and the yo-yo effect after the diet ends. For building muscle mass, a slight calorie surplus of 200–300 kcal above total energy expenditure is recommended.
Keep in mind that individual factors influence calorie needs that no formula can fully capture: thyroid function, genetic predisposition, sleep quality, hormonal changes (e.g. menopause) and certain medications. A practical method is therefore self-calibration: track your actual calorie intake for two to three weeks and observe changes in your weight. On this basis, you can determine your personal maintenance calories empirically.