BMR Calculator: Free Basal Metabolic Rate & Daily TDEE Calorie Burn
Calculate your exact Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using the clinical Mifflin-St Jeor and revised Harris-Benedict equations. Discover your daily caloric maintenance, deficit, and surplus targets.
How to Calculate Your Basal Metabolic Rate & TDEE (Step-by-Step)
Determine your resting basal caloric burn and daily energy expenditure using the clinical Mifflin-St Jeor equation in your browser:
Choose Metric (cm & kg) or Imperial (ft, in & lbs). Enter your biological sex, current age, height, and weight.
Select your lifestyle tier from Sedentary (desk job, 1.2x) to Light (1–3 days/wk, 1.375x), Moderate (3–5 days/wk, 1.55x), Very Active (6–7 days/wk, 1.725x), or Extra Active (1.9x).
Inspect your Basal Metabolic Rate (calories burned at total bed rest) and Total Daily Energy Expenditure (calories required to hold weight stable).
Check personalized calorie targets for mild fat loss (-250 kcal), standard fat loss (-500 kcal), and lean muscle gain (+300 kcal).
What is Basal Metabolic Rate (BMR) vs. Total Daily Energy Expenditure (TDEE)?
Your Basal Metabolic Rate (BMR) represents the absolute minimum quantity of energy (measured in kilocalories) your body requires to perform involuntary biological life-support functions over 24 hours. Even if you rested motionless in bed all day in a thermoneutral environment, your body would burn your exact BMR to keep your heart pumping, lungs inflating, brain synapsing, kidneys filtering, and cell membranes regulating electrolyte gradients.
In contrast, your Total Daily Energy Expenditure (TDEE) incorporates all physical motion, digestion, and daily labor atop your baseline BMR. TDEE is composed of four distinct components:
Internal cellular vitality, autonomic organ function, and basic protein synthesis.
Non-Exercise Activity Thermogenesis: pacing, typing, climbing stairs, fidgeting, and standing.
Thermic Effect of Food: the metabolic cost to digest, absorb, and metabolize ingested nutrients (highest for dietary protein at ~25%).
Exercise Activity Thermogenesis: structured athletic workouts, running, cycling, or weightlifting.
Mifflin-St Jeor vs. Harris-Benedict: Which Equation is More Accurate?
In 1919, J. Arthur Harris and Francis G. Benedict published the pioneering equation for human basal metabolism. While groundbreaking, the original formulation frequently overestimated calorie expenditure in modern sedentary populations by 5% to 15%.
In 1990, Dr. M.D. Mifflin and Dr. S.T. St Jeor published an updated predictive equation in the American Journal of Clinical Nutrition. Extensive systemic reviews by the Academy of Nutrition and Dietetics established that Mifflin-St Jeor is the most reliable equation, accurately estimating resting metabolic rate within ±10% of indirect calorimetry across both normal-weight and obese adults.
| Formula | Male Mathematical Formulation | Female Mathematical Formulation |
|---|---|---|
| Mifflin-St Jeor (1990) | 10 × W(kg) + 6.25 × H(cm) - 5 × Age + 5 | 10 × W(kg) + 6.25 × H(cm) - 5 × Age - 161 |
| Revised Harris-Benedict (1984) | 13.397 × W + 4.799 × H - 5.677 × Age + 88.362 | 9.247 × W + 3.098 × H - 4.330 × Age + 447.593 |
Metabolic Adaptation & Why You Shouldn't Crash Diet Below Your BMR
One of the most frequent mistakes made during fat loss attempts is cutting calories below Basal Metabolic Rate. When energy intake plummets below biological baseline, the endocrine system enters an evolutionary conservation state:
- Thyroid & Leptin Downregulation: Circulating active T3 thyroid hormone drops, slowing resting cellular respiration, while leptin collapses, amplifying uncontrollable appetite cravings.
- Subconscious NEAT Reduction: Without conscious awareness, your body decreases spontaneous movement, posture adjustments, and step count to preserve remaining glycogen stores.
- Skeletal Muscle Proteolysis: Unable to obtain sufficient amino acids and glucose, the body catabolizes functional muscle protein, directly shrinking your long-term metabolic engine.
To plan sustainable caloric deficits with exact protein, carb, and fat gram ratios, use our companion Calorie & Macro Calculator.
Interconnected Biometrics Suite
Combine your metabolic expenditure with our other private health calculators:
Evaluate your height-to-weight ratio against WHO standards and Asian guidelines.
calculate your BMI →Separate lean muscle tissue from adipose fat using the US Navy circumference method.
calculate your body fat percentage →Compare Devine, Robinson, Hamwi, and Miller targets for your exact height.
ideal weight for your height →Tailor your daily calorie intake and macronutrients for fat loss or muscle gains.
how many calories you need per day →Frequently Asked Questions (FAQ)
What is the exact difference between BMR and TDEE?
Basal Metabolic Rate (BMR) is the baseline energy (calories) required solely to maintain involuntary life-support functions—such as heart beating, cellular respiration, and kidney filtration—while resting completely in bed. Total Daily Energy Expenditure (TDEE) represents your complete 24-hour calorie burn, combining BMR with the thermic effect of food (TEF), non-exercise activity (NEAT), and structured physical exercise.
Why is the Mifflin-St Jeor formula preferred over the original Harris-Benedict formula?
Published in 1990 in the American Journal of Clinical Nutrition, the Mifflin-St Jeor equation was developed using modern body composition data. Extensive clinical reviews by the Academy of Nutrition and Dietetics established that Mifflin-St Jeor is the most reliable predictive equation, estimating resting metabolic rate within ±10% of indirect calorimetry, whereas older 1919 Harris-Benedict models overestimate calorie burn by 5% to 15% in sedentary modern lifestyles.
Can I eat below my Basal Metabolic Rate (BMR) to lose weight faster?
Eating below your BMR is strongly discouraged by medical guidelines. Severe caloric restriction triggers adaptive thermogenesis ('starvation response'): active T3 thyroid hormones plunge, involuntary physical fidgeting (NEAT) shuts down, and the body catabolizes functional lean muscle for fuel. A moderate deficit of 350 to 500 kcal below your TDEE (while staying near or above BMR) delivers safe, permanent fat loss.
How does building skeletal muscle increase resting metabolic rate?
Skeletal muscle is metabolically active tissue, requiring roughly 13 kcal per kilogram per day just to maintain itself at rest, compared to only 4.5 kcal per kilogram for inactive adipose fat tissue. While building 3 to 5 kg of muscle produces a modest direct BMR increase of ~40 to 65 kcal/day, the greater benefit is enhanced insulin sensitivity, higher glycogen storage capacity, and higher work capacity during exercise.
Why does Basal Metabolic Rate decrease as adults get older?
BMR naturally declines by roughly 1% to 2% per decade after age 30. This drop is primarily driven by age-related muscle loss (sarcopenia) and decreased organ metabolic mass, rather than an irreversible failure of metabolism. Engaging in regular progressive resistance training and consuming adequate protein preserves lean mass and keeps metabolic rate robust well into senior years.
How do I choose the right activity multiplier if I walk a lot at work?
If you work on your feet (e.g., nurse, teacher, waiter, construction) taking 8,000 to 12,000 daily steps, select 'Moderate Activity' (1.55) even if you do not perform structured gym workouts. High Non-Exercise Activity Thermogenesis (NEAT) frequently burns more total daily calories than a short 45-minute gym session followed by 8 hours of sedentary sitting.