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, sex, body size, and how active you are. This calorie calculator uses the Mifflin-St Jeor equation to estimate Basal Metabolic Rate (BMR) and then applies an activity factor to estimate 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 a large share of daily energy use. Your TDEE adds the calories burned through physical activity, exercise, and the thermic effect of food.
Once you know your estimated TDEE, you can sketch out rough intake ranges for maintenance, fat loss, or weight gain. These numbers are estimates, not prescriptions, so they work best as a starting point that you refine from weight trends and daily function.
Guessing your calorie needs often leads to bigger adjustments than necessary. This calculator gives you a structured estimate you can use when starting a new eating plan, returning to training, or reassessing intake after weight has changed.
It is most useful as a baseline. From there, smaller changes in intake or activity are usually easier to judge than trying to restart from scratch each time progress slows.
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: 2,759 kcal/day (maintenance)
A 30-year-old male, 80 kg, 180 cm, moderately active (exercise 3-5 days/week) has a Mifflin-St Jeor BMR of 1,780 kcal. Multiplied by the moderate activity factor of 1.55, his TDEE is approximately 2,759 kcal/day. A 500 kcal deficit gives about 2,259 kcal/day, while a lean-gain target of +300 kcal/day is about 3,059 kcal/day.
Published in 1990, the Mifflin-St Jeor equation is one of the most commonly used population-level formulas for estimating resting calorie needs. It uses weight, height, age, and sex to estimate resting energy expenditure, then relies on an activity factor to extend that estimate into daily needs.
Choosing the right activity level matters as much as choosing the formula. Sedentary usually means very little intentional exercise. Light, moderate, active, and extra active reflect progressively more movement across the week. Many people overestimate this input, so it often helps to start conservatively and adjust from results.
No calorie formula can fully account for daily variation in movement, appetite, training load, or body composition. The most useful approach is to start with the estimate, hold intake steady for a couple of weeks, and then adjust based on weight trend, hunger, energy, and performance.
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This worksheet uses the Mifflin-St Jeor equation to estimate resting calories, then applies the selected activity multiplier to estimate TDEE. The loss and gain targets shown on the page are simple adjustments around that TDEE, intended as planning ranges rather than guaranteed outcomes. Real calorie needs can shift with body composition, medication use, illness, training volume, and daily movement.
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 usually treated as a reasonable starting estimate for many adults, often within about ±10% of measured expenditure. Individual factors like genetics, hormones, medication use, and body composition can still shift the real number, so treat the result as a starting point and adjust from real-world results.
A moderate deficit below TDEE is commonly used for weight loss, with roughly 500 calories per day often cited as a practical example. The actual rate varies, and aggressive deficits are harder to sustain and may not be appropriate for everyone.
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 and on how accurate your exercise-calorie estimate is. Some people keep the original intake target, while others add back part of the session cost. A conservative approach is often easier to manage when wearable estimates are uncertain.