BMR Calculator — Basal Metabolic Rate CalculatorMifflin–St Jeor Equation · Harris-Benedict Formula · TDEE Calculator
Use this free BMR Calculator to accurately calculate your Basal Metabolic Rate (BMR) — the precise number of calories your body burns at rest to sustain essential vital physiological functions including breathing, blood circulation, cell regeneration, brain function, and hormonal regulation. This online BMR calculator uses the gold-standard Mifflin–St Jeor equation — the most clinically validated and widely recommended BMR formula by registered dietitians and nutritionists — alongside the classic Harris-Benedict BMR formula for cross-reference. Simply enter your age, gender, height, and weight to get your BMR in calories per day, then apply your Physical Activity Level (PAL) multiplier to calculate your full Total Daily Energy Expenditure (TDEE) across activity levels: Sedentary · Lightly Active · Moderately Active · Very Active · Extra Active.
Your BMR and TDEE results form the essential nutritional baseline for calculating an accurate daily calorie target tailored to your specific goal — whether that's a calorie deficit for weight loss, calorie maintenance for weight management, or a calorie surplus for muscle gain and bulking. Combined with macronutrient tracking (protein, carbohydrates, and fats), your BMR calculation becomes the foundation of any effective diet plan, meal prep strategy, or body recomposition program — used by personal trainers, sports nutritionists, and fitness coaches worldwide to design evidence-based nutrition and calorie intake plans.
⚠ Medical Disclaimer: This BMR calculator provides a scientifically based calorie estimate for informational and educational purposes only. Individual metabolic rates vary based on genetics, thyroid function, lean muscle mass, medications, and underlying health conditions. These results should not replace advice from a licensed doctor, registered dietitian (RD), or certified nutritionist. Always consult a qualified healthcare professional before making significant changes to your diet or calorie intake.
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BMR Calculator — The Calories Your Body Burns at Complete Rest
Basal Metabolic Rate is the minimum energy expenditure to sustain life at complete rest in a thermoneutral environment — the calories your organs, brain, and involuntary processes consume doing nothing else. BMR accounts for 60-75% of total daily energy expenditure for sedentary individuals. The most accurate prediction equations are Mifflin-St Jeor (developed on modern populations, ±15% error), Cunningham (better for athletes, requires lean mass), and Harris-Benedict (1919, slightly higher predictions). The BMR calculator offers all three formulas so you can compare outputs and choose the most appropriate for your situation.
BMR decreases with age at approximately 1-2% per decade after 20, largely because muscle mass declines with age and muscle is metabolically active tissue. A 60-year-old man has roughly 15-20% lower BMR than a 20-year-old of the same weight, which is why the same dietary habits that maintained weight at 25 produce gradual weight gain at 50. Resistance training that preserves or builds muscle is the primary intervention that counteracts age-related BMR decline. The calculator includes age in the formula and makes this declining trend visible.
Knowing your BMR enables precise caloric prescription. If BMR is 1,800 calories and your activity multiplier for a lightly active lifestyle is 1.375, your TDEE is 2,475 calories. Targeting 2,000 calories places you in a 475-calorie daily deficit — about 0.5 kg/week of fat loss at sustainable rate. The BMR calculator integrates with the activity multiplier to produce TDEE directly, giving you the starting number for dietary planning without a separate calculation step.