Most calorie targets you see online are guesses. Here is how to calculate a number that actually fits your body.
If you have ever Googled "how many calories do I need a day" you have probably been told 2,000 — full stop. That number is a packaging-label convention, not a personalised target. Your actual daily need can be anywhere from 1,400 to 4,000+ kcal depending on size, age, sex, muscle mass and how much you move. This guide shows you how to calculate yours.
A kilocalorie (kcal — usually just called "a calorie" in food contexts) is a unit of energy: specifically, the energy it takes to raise the temperature of 1 kg of water by 1°C. Your body uses calories to keep your heart beating, your brain firing, your muscles moving, and even to digest the food itself.
Basal Metabolic Rate (BMR) is the energy your body burns at complete rest — what you would need if you stayed in bed all day. It accounts for roughly 60–70% of total daily expenditure for most people. The most accurate everyday formula is the Mifflin-St Jeor equation:
Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Example — a 35-year-old man, 80 kg, 178 cm: BMR = 800 + 1,112.5 − 175 + 5 = 1,742.5 kcal/day at total rest.
Total Daily Energy Expenditure (TDEE) multiplies your BMR by an activity factor:
Same 35-year-old man, lightly active: TDEE = 1,742.5 × 1.375 ≈ 2,396 kcal/day.
Eat about that many calories and your weight stays stable.
Avoid the temptation to crash-diet below ~1,200 kcal (women) or ~1,500 kcal (men). Below that, your body slows your metabolism, you lose muscle, and you set yourself up for rebound weight gain.
Calories tell you how much energy is in your food, not what it does to your body. 200 kcal of broccoli, 200 kcal of chicken breast and 200 kcal of cola behave very differently — for hunger, blood sugar, insulin, micronutrients and long-term health. A useful target: get most calories from minimally processed foods, hit your protein target (around 1.6 g per kg of bodyweight if you train), and treat ultra-processed snacks as occasional, not staple.
Why do online calculators give different numbers? They use different equations (Mifflin-St Jeor, Harris-Benedict, Katch-McArdle). Pick one and stick with it for 4 weeks before judging.
Do I need fewer calories as I age? Slightly — mostly because muscle mass tends to drop. You can offset most of the age effect by resistance training.
Does cold weather burn more calories? A small amount, through thermogenesis. Not enough to plan a diet around.
Try our free TDEE Calculator — it asks for your stats, returns your maintenance and goal calories, and remembers your country's preferred units.