BMR Calculator : Free Basal Metabolic Rate & TDEE Tool
Calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) in real time. Compare the clinical Mifflin-St Jeor, Revised Harris-Benedict, and Katch-McArdle formulas with custom calorie targets for fat loss and muscle gain.
To calculate Basal Metabolic Rate (BMR), use the clinical Mifflin-St Jeor equation. For men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5. For women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161. This measures baseline calories burned at complete physical rest.
| Activity Level | Multiplier | Daily TDEE (Maintenance) | Weight Loss (-500 kcal) |
|---|
BMR vs. TDEE: How the Human Body Burns Energy
Total human energy expenditure consists of four distinct metabolic processes:
- Basal Metabolic Rate (BMR ∼60–70%): The involuntary energy required to sustain life at complete physical and digestive rest (maintaining cellular respiration, brain function, liver protein synthesis, and body temperature).
- Non-Exercise Activity Thermogenesis (NEAT ∼15%): Unconscious daily movement, including walking, typing, maintaining posture, and spontaneous fidgeting.
- Thermic Effect of Food (TEF ∼10%): The caloric cost of chewing, digesting, absorbing, and storing nutrients (dietary protein burns 20–30% of its calories during digestion, compared to only 5–10% for carbohydrates).
- Exercise Activity Thermogenesis (EAT ∼5–10%): Deliberate cardiovascular training and resistance exercise.
Total Daily Energy Expenditure (TDEE) sums all four components. To lose body fat, you must establish an energy deficit relative to your TDEE—not your BMR.
Clinical BMR Formulas Compared
| Equation | Primary Variables | Accuracy Margin | Optimal Application |
|---|---|---|---|
| Mifflin-St Jeor (1990) | Weight, Height, Age, Sex | ±10% of indirect calorimetry | Clinical standard for general adult populations. |
| Katch-McArdle (1996) | Lean Body Mass (LBM) Only | Highest for athletes | Athletes and individuals with measured body fat. |
| Revised Harris-Benedict (1984) | Weight, Height, Age, Sex | ±15% (Tends to overestimate) | Historical clinical baseline. |
How to Structure Your Daily Macronutrients
Once your target daily calorie intake is calculated, divide your energy across the three primary macronutrients to preserve lean muscle tissue while losing adipose fat:
- Dietary Protein (4 kcal/g): Prioritize 1.6 to 2.2 grams per kilogram of body weight (0.8–1.0g per lb). Adequate protein spares skeletal muscle during a caloric deficit and maximizes satiety.
- Dietary Fats (9 kcal/g): Allocate 20% to 30% of total daily calories to healthy fats to support hormone production, vitamin absorption (A, D, E, K), and endocrine function.
- Carbohydrates (4 kcal/g): Fill the remaining daily caloric budget with complex carbohydrates to replenish glycogen reserves and fuel training performance.
Related Health & Anthropometric Calculators:
- Body Fat Percentage Calculator — Calculate lean mass and fat mass using the U.S. Navy circumference method.
- Ideal Weight Calculator — Calculate target weight using Devine, Robinson, and Miller equations.
- Body Mass Index (BMI) Calculator — Official WHO adult and child BMI category calculator.
- BMI Clinical Limitations Guide — Quetelet math vs. visceral adipose distribution.
Frequently Asked Questions
What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the minimum energy your body burns to stay alive at complete rest. TDEE (Total Daily Energy Expenditure) is your actual total daily calorie burn, calculated by multiplying your BMR by your physical activity factor.
Should I eat fewer calories than my BMR to lose weight?
No. Eating below your BMR is generally not recommended without physician supervision. Severe caloric restriction deprives vital organs of energy, slows thyroid hormone production, downregulates spontaneous activity (NEAT), and causes muscle loss.
Why is the Katch-McArdle formula more accurate for athletes?
The Katch-McArdle equation calculates metabolic rate based purely on Lean Body Mass (LBM) rather than total weight. Because muscle tissue burns significantly more resting energy than adipose fat, Katch-McArdle prevents underestimating energy needs in muscular individuals.
How many calories should I cut to lose 1 pound per week?
One pound of human adipose fat contains approximately 3,500 calories. A daily caloric deficit of 500 calories below your maintenance TDEE produces roughly 1 pound of fat loss per week (500 kcal × 7 days = 3,500 kcal).
Is my health data saved or logged?
No. All calculations execute 100% locally inside your browser's runtime memory using JavaScript. No personal biometric measurements or health stats are sent across an HTTP network or saved in an external database.