Your daily calorie needs depend on multiple factors including age, gender, weight, height, and activity level. Understanding these numbers is essential for achieving any health goal, whether weight loss, maintenance, or muscle gain. Your Total Daily Energy Expenditure (TDEE) represents all calories you burn in a day through basic bodily functions plus physical activity.

Basal Metabolic Rate (BMR) is the number of calories your body burns at rest to maintain vital functions like breathing, circulation, and cell production. BMR typically accounts for 60-75% of your total daily calorie burn. The Mifflin-St Jeor equation, used by this calculator, is considered the most accurate formula for estimating BMR in healthy adults.

Your TDEE is calculated by multiplying your BMR by an activity factor that accounts for exercise and daily movement. Sedentary individuals (little to no exercise) multiply BMR by 1.2, while very active people (intense exercise 6-7 days/week) use a factor of 1.725. Most people overestimate their activity level, so be honest when selecting your activity factor to get accurate calorie targets.

To lose one pound of body fat, you need a caloric deficit of approximately 3,500 calories. A safe, sustainable weight loss rate is 1-2 pounds per week, requiring a daily deficit of 500-1,000 calories. Larger deficits can lead to muscle loss, nutritional deficiencies, metabolic slowdown, and difficulty maintaining weight loss long-term. Never eat below 1,200 calories/day (women) or 1,500 calories/day (men) without medical supervision.

Sedentary (1.2): Little to no exercise, desk job, minimal walking or movement throughout the day. You spend most of your time sitting and don't have a regular exercise routine. This describes most office workers who don't intentionally exercise. Examples: sitting at a desk 8 hours/day, driving long distances, watching TV in the evening.

Lightly Active (1.375): Light exercise or sports 1-3 days per week, or an active job that involves standing and walking. You might take walks, do light yard work, or have a job that keeps you on your feet. Examples: retail workers, servers, light jogging 2-3 times per week, yoga or stretching classes.

Moderately Active (1.55): Moderate exercise or sports 3-5 days per week. You have a consistent exercise routine that includes cardio and/or strength training. Examples: running 3-4 times per week, cycling, swimming, playing recreational sports, gym workouts combining cardio and weights.

Very Active (1.725): Hard exercise or sports 6-7 days per week, or a physically demanding job plus regular exercise. You're very consistent with intense workouts and/or have a job that requires constant physical labor. Examples: construction workers, athletes in training, competitive cyclists, CrossFit enthusiasts training daily.

Extra Active (1.9): Very hard exercise or physical job plus intense training, or training twice per day. This level is for serious athletes, military personnel in active training, or those with extremely demanding physical jobs who also train intensely. Most people don't fall into this category. Examples: marathon training, bodybuilding prep, professional athletes, military training programs.

For Weight Loss: Create a calorie deficit of 500-1,000 calories per day to lose 1-2 pounds per week. Start with a 500-calorie deficit and monitor your progress. If you're not losing weight after 2-3 weeks, reduce calories by another 100-200 or increase activity. Focus on nutrient-dense, filling foods like vegetables, lean proteins, and whole grains to feel satisfied while eating less.

For Weight Maintenance: Eat approximately your TDEE to maintain your current weight. Your weight may fluctuate 2-3 pounds day-to-day due to water retention, food volume, and hormone changes—this is normal. Track your average weight over 2-4 weeks to assess if you're truly maintaining. Adjust calories by 100-200 if you notice a consistent trend up or down.

For Weight Gain: Create a calorie surplus of 250-500 calories per day to gain 0.5-1 pound per week. Larger surpluses lead to excessive fat gain rather than muscle. Combine your surplus with strength training 3-5 times per week to maximize muscle growth. Focus on protein (0.7-1g per pound of body weight), complex carbs for energy, and healthy fats for hormones.

Track and Adjust: Use a food tracking app like MyFitnessPal or Cronometer for at least 2-4 weeks to understand portion sizes and your actual intake. Most people underestimate calories by 20-40% without tracking. Weigh yourself weekly at the same time (morning, after bathroom, before eating) and adjust calories based on progress. If you're not seeing results after 3-4 weeks, reassess your activity level, tracking accuracy, or calorie target.

Consider Metabolic Adaptation: As you lose weight, your TDEE decreases because you have less body mass to maintain. Recalculate your calorie needs every 10-15 pounds lost or if your progress stalls for 3+ weeks. This is why weight loss slows over time—it's not a plateau, it's physics. You may need to eat less or move more as you get leaner.