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BMR Calculator

Calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) with 100% scientific accuracy using verified Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle equations.

Measurement Units
15 – 100 years
years
kg
cm
e.g. 15%
%

Unlocks the Lean Body Mass Katch-McArdle formula for athletes and bodybuilders.

Calculated Metabolic Results
Basal Metabolic Rate (BMR)mifflin
1,730kcal / day

Minimum calories burned at complete rest to sustain life.

Daily Energy Burn (TDEE)1.55× Active
2,682kcal / day

Calories burned including your daily physical activity.

Formula Comparison:
Mifflin: 1730 kcal•Harris: 1787 kcal

Daily Calorie Targets by Goal

Select a goal below to view tailored macronutrient distribution.

Energy Balance
Maintain WeightBaseline
2,682 kcal0 kg / week (Current Weight)
Mild Weight Loss-250 kcal
2,432 kcal-0.25 kg (-0.5 lb) / week
Standard Weight Loss-500 kcal
2,182 kcal-0.50 kg (-1.0 lb) / week
Intense Weight Loss-1000 kcal
1,682 kcal-1.00 kg (-2.0 lb) / week
Mild Weight Gain+250 kcal
2,932 kcal+0.25 kg (+0.5 lb) / week
Standard Weight Gain / Bulking+500 kcal
3,182 kcal+0.50 kg (+1.0 lb) / week

Macronutrient Breakdown

Daily protein, carbs, and fat for target: 2,682 kcal

Protein (30%)
201g
805 kcal
Carbs (40%)
268g
1073 kcal
Fat (30%)
89g
805 kcal

Ideal for general health, energy balance, and everyday well-being (4 kcal/g protein, 4 kcal/g carbs, 9 kcal/g fat).

Activity Multipliers & Daily Burn Comparison

Sedentary
1.2×2,076 kcal
Lightly Active
1.375×2,379 kcal
Moderately Active
1.55×2,682 kcal
Very Active
1.725×2,984 kcal
Extremely Active
1.9×3,287 kcal
Metabolic Science

What is Basal Metabolic Rate (BMR)?

Understanding how your body burns fuel at rest is the foundation of effective body recomposition, weight loss, and athletic performance.

Basal Metabolic Rate (BMR) represents the baseline energy expenditure—measured in kilocalories (kcal) per 24-hour cycle—necessary to sustain life in a post-absorptive state while resting in a thermo-neutral room. Even when you are completely immobile or sleeping, your vital organs consume massive amounts of energy to keep you alive.

Where Do Your Resting Calories Actually Go?

27%LiverFiltration & synthesis
19%BrainIon pumps & signaling
18%Skeletal MuscleTone & protein turnover
10%KidneysBlood purification
7%HeartContinuous pumping
19%Other TissueLungs, gut & skin

Your BMR typically accounts for 60% to 75% of your total daily caloric expenditure. The remaining calories are burned through the Thermic Effect of Food (TEF, ~10%) and physical movement (both structured exercise and spontaneous activity like walking and fidgeting, termed NEAT).

BMR vs. RMR vs. TDEE: What Is the Difference?

Fitness terminology frequently confuses these three metrics. Here is the clinical distinction:

Strict Clinical Standard

BMR (Basal Metabolic Rate)

Measured in a lab immediately upon waking after 8 hours of sleep and a 12-hour fast, with zero physical movement. It is the absolute biological floor.

60% – 70% of Daily Burn
Resting Metric

RMR (Resting Metabolic Rate)

Measured in less restrictive conditions without overnight fasting. Because slight digestive activity and low-level movement are present, RMR is typically 5% to 10% higher than BMR.

BMR + ~5-10%
Total Daily Burn

TDEE (Total Daily Expenditure)

The total energy consumed throughout the entire day: BMR + Exercise + Non-Exercise Physical Activity (NEAT) + Digestion (TEF). This is your actual maintenance calorie requirement.

BMR × 1.2 to 1.9 Multiplier
Formula Mechanics

The Science & Equations Behind BMR Calculation

Zobinzo employs the three most heavily cited, peer-reviewed clinical predictive equations in nutritional medicine.

1Mifflin-St Jeor Equation (1990)

Gold Standard

Published by MD Mifflin and ST St Jeor in the American Journal of Clinical Nutrition, this formula is regarded by the American Dietetic Association as the most reliable predictive formula for modern populations.

Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161

2Revised Harris-Benedict Equation (Roza & Shizgal, 1984)

Clinical Classic

The original 1919 study was recalibrated in 1984 by Roza and Shizgal using modern indirect calorimetry equipment. It remains heavily utilized in hospital dietetics.

Men: BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) − (5.677 × age)
Women: BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) − (4.330 × age)

3Katch-McArdle Formula (Lean Mass Based)

Athletes & Bodybuilders

Unlike equations based solely on total scale weight, Katch-McArdle utilizes your specific Lean Body Mass (LBM). This avoids underestimating metabolic burn in muscular individuals or overestimating in individuals carrying higher adiposity.

Step 1 (LBM): Lean Body Mass (kg) = Weight (kg) × (1 − [Body Fat % / 100])
Step 2 (BMR): BMR = 370 + (21.6 × LBM in kg)

Biological Factors That Influence Your BMR

Why do two people of identical weight burn calories at different rates? Several primary biological factors govern your baseline burn:

Muscle Mass to Fat Ratio

Muscle tissue is metabolically active, burning roughly 6 kcal per pound per day at complete rest, compared to 2 kcal for adipose fat. Increasing skeletal muscle mass permanently elevates your baseline burn.

Age & Sarcopenia

Metabolic rate declines by roughly 1% to 2% per decade after age 20. Much of this drop is not inevitable aging, but rather age-related muscle loss (sarcopenia), which can be prevented with resistance training.

Thyroid & Endocrine Function

The thyroid gland produces thyroxine (T4) and triiodothyronine (T3), the primary hormones regulating cellular metabolism. Hypothyroidism slows BMR, while hyperthyroidism accelerates it.

Thermic Effect of Food (TEF)

Digesting dietary protein burns 20% to 30% of its caloric value in metabolic heat, compared to 5–10% for carbohydrates and 0–3% for dietary fats. High-protein diets naturally increase daily expenditure.

How to Use BMR to Lose, Maintain, or Gain Weight

Energy balance is governed by the First Law of Thermodynamics: Calories In vs. Calories Out (CICO). Here is how to apply your BMR & TDEE numbers strategically:

Fat Loss Strategy

Establish a moderate 300 to 500 kcal deficit below your TDEE. Never drop below your BMR for prolonged periods to avoid triggering adaptive thermogenesis and muscle loss.

Weight Maintenance

Consume 100% of your calculated TDEE. This stabilizes weight and hormone levels, providing optimal energy for athletic performance and daily recovery.

Lean Bulking Strategy

Consume a controlled surplus of 250 to 500 kcal above TDEE paired with heavy resistance training to maximize muscle protein synthesis while keeping fat gain minimal.

Common Questions

Frequently Asked Questions

Everything you need to know about metabolism, calorie deficits, formulas, and activity tracking.

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