Estimate your daily calorie needs (BMR and TDEE) based on age, gender, height, weight, and activity level. Get targets for weight loss, maintenance, and muscle gain.
How many calories should you eat per day? The answer depends on your age, gender, body size, and how active you are. This calorie calculator uses the Mifflin-St Jeor equation — widely considered the most accurate formula for estimating Basal Metabolic Rate (BMR) — and multiplies it by an activity factor to give you your Total Daily Energy Expenditure (TDEE).
Your BMR is the number of calories your body burns at complete rest just to keep you alive: breathing, circulating blood, maintaining body temperature, and repairing cells. It accounts for 60-75% of total daily calories. Your TDEE adds the calories burned through physical activity, exercise, and the thermic effect of food (digestion).
Once you know your TDEE, you can set precise targets: eat at TDEE to maintain weight, eat 500 calories below TDEE to lose roughly 1 pound per week, or eat 300-500 above TDEE to gain lean mass. These numbers are estimates — individual metabolism varies by 5-10% — but they provide a scientifically grounded starting point for any nutrition plan.
Guessing your calorie needs leads to frustration. Eat too little and you lose muscle, feel exhausted, and eventually binge. Eat too much and you gain unwanted fat. This calculator eliminates the guesswork by giving you a personalized number based on established scientific formulas.
It is especially valuable when starting a new diet, beginning a fitness program, or hitting a weight-loss plateau. By knowing the actual numbers, you can make small, informed adjustments (reduce by 200 calories, increase activity by one level) rather than drastic, unsustainable changes.
Mifflin-St Jeor Equation: Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + 5 Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) − 161 TDEE = BMR × Activity Multiplier Sedentary (little/no exercise): × 1.2 Lightly active (1-3 days/week): × 1.375 Moderately active (3-5 days/week): × 1.55 Very active (6-7 days/week): × 1.725 Extra active (2× per day): × 1.9
Result: 2,687 kcal/day (maintenance)
A 30-year-old male, 80 kg, 180 cm, moderately active (exercise 3-5 days/week) has a BMR of 1,734 kcal. Multiplied by the moderate activity factor of 1.55, his TDEE is approximately 2,687 kcal/day. To lose 1 lb/week, he should eat ~2,187 kcal. To gain lean mass, ~3,000-3,187 kcal.
Published in 1990, the Mifflin-St Jeor equation replaced the older Harris-Benedict equation (1919) as the most accurate BMR formula for modern populations. It accounts for the fact that people today tend to have different body compositions than a century ago. The formula uses weight (kg), height (cm), age (years), and sex to estimate resting calorie burn.
Choosing the right activity level is crucial. Sedentary means desk job with no exercise. Lightly active means light exercise 1-3 days per week, like walking or casual cycling. Moderately active means structured exercise 3-5 days (gym sessions, running, sports). Very active means intense exercise 6-7 days. Extra active is for athletes or those with very physical jobs who also train. Most people overestimate their activity level — when in doubt, choose one level lower.
One pound of body fat contains approximately 3,500 calories. To lose one pound per week, you need a cumulative deficit of 3,500 calories — or 500 per day. This can come from eating less, moving more, or both. Research consistently shows that combining a moderate calorie deficit with regular exercise produces the best long-term results, preserving muscle while losing fat.
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain life-sustaining functions — breathing, heartbeat, brain function, cell repair. It represents 60-75% of total daily energy expenditure and is influenced by age, sex, weight, height, and genetics.
Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor. It represents all the calories you burn in an average day, including exercise, walking, fidgeting, and digesting food. Eating at your TDEE maintains your current weight.
It is accurate within ±10% for most adults, making it the best available formula according to the Academy of Nutrition and Dietetics. Individual factors like genetics, hormones, and body composition can cause variation. Treat the result as a starting point and adjust based on real-world results.
A deficit of 500 calories below your TDEE typically results in 1 pound of fat loss per week. For faster loss, a 750 kcal deficit yields about 1.5 lbs/week. Never go below 1,200 kcal/day (women) or 1,500 kcal/day (men) without medical supervision.
Activity can add 20-90% on top of BMR. A sedentary person burns 20% more than BMR; a very active person nearly doubles it. This is why exercise is so effective — it substantially increases calorie burn beyond baseline.
Yes, but less than people think. BMR decreases about 1-2% per decade after age 20, primarily due to loss of muscle mass. Strength training can largely offset this decline by maintaining or building lean tissue.
It depends on your goal. If you are trying to lose weight, eating back only half of exercise calories provides a safety margin (since calorie burn estimates are often overstated). If maintaining or building muscle, eating back most or all ensures adequate fuel.