Your result includes three key values: Basal Metabolic Rate (BMR), Total Daily Energy Expenditure (TDEE), and a goal-adjusted target. BMR is the number of calories your body burns at complete rest just to maintain basic functions like breathing, circulation, and cell production. TDEE is your BMR multiplied by an activity factor and represents how many calories you actually burn in a typical day including physical activity. The goal-adjusted target adds or subtracts 500 calories from your TDEE depending on whether you selected weight loss or weight gain.

For weight loss, the 500 kcal/day deficit translates to roughly 0.5 kg (1 lb) of fat loss per week, which is widely considered a safe and sustainable rate. For weight gain, a 500 kcal/day surplus similarly promotes about 0.5 kg/week of gain, ideally combined with resistance training to favor lean mass. If your calculated target falls below 1200 kcal/day for women or 1500 kcal/day for men, you should consult a healthcare provider before proceeding, as very low calorie diets require medical supervision.

Keep in mind that these are estimates. Actual caloric needs vary based on genetics, body composition, hormonal status, and metabolic adaptation. Use this as a starting point and adjust based on real-world results over 2-4 weeks.

Use this calculator when you want a science-based starting point for daily calorie intake, whether your goal is weight loss, maintenance, or muscle gain. It is particularly helpful when beginning a structured diet or exercise program and you need a caloric target to plan meals around. Clinicians and dietitians frequently use the Mifflin-St Jeor equation as a first step in nutritional counseling because it is the most accurate predictive equation for resting metabolic rate in both normal-weight and obese individuals.

This tool is also useful for tracking how caloric needs change over time. As you lose or gain weight, your BMR changes, and recalculating periodically (every 4-8 weeks) helps you avoid plateaus. Athletes and active individuals can use it to ensure they are fueling adequately for training demands.

The Mifflin-St Jeor equation was developed from a population of healthy adults and may be less accurate at the extremes of age, body size, or fitness. It does not account for individual metabolic variation, which can differ by 10-15% between people of the same size, age, and sex. It also does not distinguish between fat mass and lean mass, so highly muscular individuals may have higher actual BMR than predicted.

Activity level selection is inherently subjective and is a common source of error. Most people overestimate their activity level, which can lead to consuming more calories than intended. When in doubt, select one level lower than you think applies to you.

This calculator does not account for medical conditions that affect metabolism, such as hypothyroidism, Cushing syndrome, or polycystic ovary syndrome. It also does not factor in medications (e.g., corticosteroids, certain antidepressants) that can alter metabolic rate or appetite. For individuals with these conditions, guidance from a healthcare provider or registered dietitian is essential.