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Printed on 6/29/2026
For informational purposes only. This is not medical advice.
The Calorie Calculator estimates your daily caloric needs using the Mifflin-St Jeor equation, which is considered the most accurate resting metabolic rate (RMR) formula. It accounts for your weight, height, age, sex, and activity level to calculate your Basal Metabolic Rate (BMR), then multiplies by an activity factor to determine your [Total Daily Energy Expenditure](/tools/tdee-calculator) (TDEE). You can then adjust for your goal — weight loss (−500 kcal/day ≈ 0.5 kg/week loss), maintenance, or weight gain (+500 kcal/day ≈ 0.5 kg/week gain).
Formula: BMR (Male) = 10×weight + 6.25×height − 5×age + 5. BMR (Female) = 10×weight + 6.25×height − 5×age − 161. TDEE = BMR × Activity Factor.
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Input your age, sex, height, and weight. These four values are used to calculate your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation — for men: (10×kg + 6.25×cm − 5×age + 5); for women: (10×kg + 6.25×cm − 5×age − 161).
Choose the multiplier that reflects your typical weekly activity: sedentary (1.2), lightly active (1.375), moderately active (1.55), active (1.725), or very active (1.9). Your BMR is multiplied by this factor to estimate your Total Daily Energy Expenditure (TDEE).
Your TDEE is your maintenance calorie level. Subtract 500 kcal/day for approximately 0.5 kg/week of weight loss, or add 500 kcal/day for weight gain. The calculator displays all three targets so you can choose based on your goal.
Dieters & anyone with weight goals
Get a science-based calorie target for weight loss or gain. A 500 kcal daily deficit produces ~0.5 kg/week of fat loss — the most sustainable rate according to dietetic guidelines. Pair with the [Macro Calculator](/tools/macro-calculator) for a complete nutrition plan.
Athletes & active individuals
Determine maintenance calories before planning a training-phase surplus or competition-cut deficit. Athletes need accurate TDEE to avoid RED-S (relative energy deficiency in sport) while meeting performance demands.
Registered dietitians & nutritionists
The Mifflin-St Jeor equation is the AND-recommended formula for initial patient caloric assessment. Use it as the first step in outpatient nutrition counseling or before referring to indirect calorimetry.
Bariatric surgery patients & teams
Calculate caloric targets during the staged reintroduction of food after gastric bypass or sleeve gastrectomy, where intake is highly restricted and must be monitored against metabolic needs.
Eating disorder treatment teams
Support refeeding guidance in anorexia nervosa recovery by estimating maintenance calories. Gradual caloric increases above calculated BMR reduce refeeding syndrome risk while supporting weight restoration.
Anyone tracking weight over time
As weight changes, so does BMR. Recalculate every 4–8 weeks during active weight loss to update targets. A 10 kg loss can reduce TDEE by 200–300 kcal/day, explaining common plateaus.
Harris-Benedict (1919) overestimates RMR by about 5% in most adults. Mifflin-St Jeor (1990) is more accurate across normal-weight and obese populations. Most modern nutrition software now defaults to Mifflin-St Jeor for this reason.
Most people overestimate their activity level. If you sit at a desk but go to the gym 3×/week, you're likely 'lightly active' not 'moderately active.' When in doubt, select one level lower — it's easier to add calories than undo overeating.
One pound of fat is approximately 3,500 kcal. A 500 kcal/day deficit sustains ~0.5 kg/week loss. This rate preserves muscle and is considered safe and sustainable. Deficits >1,000 kcal/day risk lean mass loss.
For BMR calculation in extremely obese patients, current body weight is the correct input — not ideal body weight (IBW). Fat tissue is metabolically active and contributes to energy expenditure. Using IBW underestimates caloric needs.
After sustained calorie restriction, BMR decreases ~15% beyond what weight loss alone explains. This adaptive thermogenesis is why diet breaks (eating at maintenance for 1–2 weeks) can help restart weight loss.
Alternating higher-calorie and lower-calorie days ('zigzag dieting') — while maintaining the same weekly total — may partially prevent the metabolic slowdown seen with continuous restriction.
Protein at 1.6–2.2 g/kg/day during calorie restriction significantly preserves lean mass. Use the [Protein Intake Calculator](/tools/protein-intake) to set your protein floor before allocating remaining calories to carbs and fat.
Diets below 800 kcal/day can cause serious complications including cardiac arrhythmias, electrolyte disturbances, and gallstones. Never recommend or follow a VLCD without specialist oversight.
BMR decreases approximately 1–2% per decade after age 30, primarily due to loss of lean muscle mass (sarcopenia). Resistance training can partially offset this by maintaining muscle, which is metabolically active tissue.
Equations are population averages. Individual metabolic variation is ±200–300 kcal/day. Adjust based on real-world weight trends over 2–3 weeks rather than assuming the calculator is precisely right.
Mifflin-St Jeor equation developed by Mifflin et al. (J Am Diet Assoc 1990). A systematic review by Frankenfield et al. (J Am Diet Assoc 2005) found it the most accurate predictive equation (±10%) for measured RMR in healthy adults. Harris-Benedict equation (1919) overestimates RMR by ~5%. Activity multipliers from Ainsworth et al. compendium and AND 2016 position statement on nutrition for weight management.
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. Once you have your calorie target, use our [Macro Calculator](/tools/macro-calculator) to split calories into protein, carbs, and fat.
This tool is also useful for tracking how caloric needs change over time. As you lose or gain weight, your [BMI](/tools/bmi-calculator) and BMR change, 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.
Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.
April 21, 2026 · trust-baseline
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