Calculate your baseline daily energy expenditure at complete rest. Choose from Mifflin-St Jeor, Harris-Benedict, or Katch-McArdle formulas.
A professional nutritionist designing an athlete's meal plan must establish their baseline metabolic needs. Human energy expenditure consists of three key components: resting metabolic rate, the thermic effect of food digestion, and physical activity. Resting metabolism accounts for 60% to 75% of total daily energy output.
Basal Metabolic Rate (BMR) represents the absolute minimum amount of energy needed to sustain life-supporting functions when your body is at complete physical, mental, and digestive rest. These processes include pumping blood, breathing, maintaining body temperature, synthesizing hormones, and cell regeneration. Measuring BMR requires strict clinical conditions, typically after 12 hours of fasting and immediately upon waking in a temperature-controlled room.
Mathematical equations approximate BMR using variables like gender, age, weight, and height. Because testing BMR in a clinical lab is complex, these equations serve as reliable estimates for fitness, diet, and clinical planning.
Proposed in 1990 by MD Mifflin and ST Jeor, this formula represents the current industry standard. It is recommended by the Academy of Nutrition and Dietetics for its high reliability in normal-weight and obese adults.
// 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) - 161Originally published in 1918 by JA Harris and FG Benedict, this classic formula was updated in 1984 by AM Roza and HM Shizgal. While popular, it can overestimate baseline needs in some groups compared to modern standards.
// Men (Revised)
BMR = 13.397 × weight (kg) + 4.799 × height (cm) - 5.677 × age (years) + 88.362
// Women (Revised)
BMR = 9.247 × weight (kg) + 3.098 × height (cm) - 4.330 × age (years) + 447.593This formula requires body fat measurements. By focusing on lean body mass rather than total weight, it offers precise numbers for athletes and bodybuilders who deviate from average body composition structures.
BMR = 370 + 21.6 × Lean Body Mass (kg)
LBM = total weight × (1 - body fat % / 100)Body Composition: Muscle tissue is metabolically active. One pound of muscle burns roughly 6 calories per day at rest, whereas a pound of fat burns about 2 calories. Increasing lean muscle mass elevates your baseline metabolic rate.
Age: BMR decreases by approximately 2% to 3% per decade during adulthood. This shift occurs due to natural age-related sarcopenia (loss of muscle tissue) and shifts in hormonal baseline levels.
Gender: Men generally have higher BMR values than women of similar height and weight because they typically possess more skeletal muscle tissue and lower average body fat ratios.
Genetics and Thyroid Health: Thyroxine, secreted by the thyroid gland, regulates cellular respiration and metabolic rate. Hypothyroidism slows resting metabolism, while hyperthyroidism accelerates it.
BMR does not account for daily movement or exercise. To calculate actual daily caloric needs, you must multiply your BMR by an activity multiplier. This resulting figure is your Total Daily Energy Expenditure (TDEE). If you consume fewer calories than your TDEE, your body uses stored energy reserves, resulting in weight loss. Eating more than your TDEE yields a caloric surplus, promoting weight gain.
| Formula | Best Used For | Requires Body Fat % | Recommended Standard |
|---|---|---|---|
| Mifflin-St Jeor | Standard adults | No | Yes (ADA standard) |
| Katch-McArdle | Athletes & lean individuals | Yes | Highly recommended for bodybuilders |
| Harris-Benedict | Comparison against historic datasets | No | No (often replaced by Mifflin) |
BMR is measured under strict laboratory conditions following a 12-hour fast, immediately upon waking. Resting Metabolic Rate (RMR) is measured under less restrictive guidelines and includes energy spent on recent digestion and light movement, making RMR slightly higher than BMR.
Yes. Chronic calorie restriction can trigger adaptive thermogenesis. Your body slows its metabolic rate to conserve energy. This makes moderate calorie deficits more sustainable than severe restriction.
Yes. This calculator converts pounds to kilograms (1 lb = 0.453592 kg) and inches to centimeters (1 inch = 2.54 cm) before applying standard formulas, ensuring precision.
BMI Calculator — Checks weight classifications based on WHO height and weight standards.
TDEE Calculator — Combines BMR with activity factors to determine daily maintenance calorie needs.
Ideal Weight Calculator — Compares historical standards for body weight targets.