How your calorie needs are calculated
Two steps: first your BMR (basal metabolic rate — calories burned at complete rest) with the Mifflin-St Jeor equation, the formula most consistently validated against measured energy expenditure:
- Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
- Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Then TDEE = BMR × activity multiplier. The multipliers above come from standard physical-activity level (PAL) research and range from 1.2 for desk-bound days to 1.9 for athletes training twice daily.
Turning TDEE into a goal
One kilogram of body fat stores roughly 7,700 kcal, so a daily deficit of 500 kcal produces about 0.5 kg of loss per week. Faster deficits tend to cost more muscle and adherence, which is why 0.25–0.75% of body weight per week is the usual recommendation.
Important limits
Most guidelines advise staying above roughly 1,200 kcal/day (women) and 1,500 kcal/day (men) without medical supervision. Very low intakes slow metabolism, increase muscle loss and raise the risk of nutrient deficiencies. This calculator gives estimates, not prescriptions — consult a clinician before aggressive dieting.