Calorie & BMR Calculator (Mifflin–St Jeor)
Estimate basal metabolic rate and daily calorie needs from height, weight, age, sex, and activity level, with targets for losing or gaining weight.
BMR and daily calorie needs
Basal metabolic rate is the energy your body uses at complete rest just to stay alive — breathing, circulation, brain activity, keeping warm. It's the floor of your daily needs, and it's usually 60–70% of the total.
Men: BMR = 10w + 6.25h − 5a + 5
Women: BMR = 10w + 6.25h − 5a − 161
With weight in kg, height in cm, and age in years. This is theMifflin–St Jeor equation, generally considered the most accurate of the simple formulas for the general population.
From BMR to TDEE
Multiply BMR by an activity factor — from 1.2 for sedentary up to 1.9 for very physical work — and you get total daily energy expenditure, the calories to maintain your current weight. Changing weight means eating consistently above or below that figure.
Why the deficit targets look like they do
A kilogram of body fat stores roughly 7700 kcal, so losing 0.5 kg a week needs about a 550 kcal daily deficit. That's the arithmetic behind the targets above. In practice weight loss rarely tracks the maths exactly: metabolism adapts, water weight fluctuates, and calorie labels and estimates both carry error.
Worked example
A 30-year-old man, 175 cm and 70 kg: BMR = 700 + 1093.75 − 150 + 5 ≈ 1649 kcal. Moderately active (×1.55) gives about 2555 kcal to maintain weight, or roughly 2005 kcal to lose half a kilo a week.
These are population-average estimates, not medical or dietary advice. Individual metabolism varies substantially, and very low calorie intakes can be harmful. Consult a doctor or registered dietitian before making significant changes, especially with any health condition, or if pregnant or breastfeeding.