Understanding BMR and TDEE: Your Metabolism Explained

CalculatorGlobe Team February 25, 2026 14 min read Health

Your body burns calories around the clock, even while you sleep. Understanding exactly how many calories your body needs starts with two fundamental concepts: Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE). Together, these numbers form the foundation for any nutrition plan, whether your goal is to lose weight, gain muscle, or simply maintain your current physique.

In this guide, you will learn what BMR and TDEE mean, how to calculate each using scientifically validated formulas, see real-world examples, and discover the factors that influence your metabolism. By the end, you will have the knowledge to make informed decisions about your calorie intake.

What Is BMR?

Basal Metabolic Rate (BMR) is the number of calories your body requires to maintain basic life-sustaining functions while at complete rest. These functions include breathing, blood circulation, cell production, nutrient processing, and maintaining body temperature. BMR represents the absolute minimum energy your body needs to stay alive if you were to lie motionless in bed all day.

For most adults, BMR accounts for approximately 60% to 75% of total daily calorie expenditure. This means the majority of the calories you burn each day are not from exercise or physical activity, but from keeping your organs functioning and your body temperature regulated. A typical adult male has a BMR between 1,600 and 2,000 calories, while a typical adult female falls between 1,200 and 1,600 calories, though individual variation is significant.

BMR is measured under strict clinical conditions: after at least 8 hours of sleep, 12 hours of fasting, lying still in a temperature-neutral environment. Because these conditions are difficult to replicate outside a lab, most calculators actually estimate Resting Metabolic Rate (RMR), which is measured under slightly less restrictive conditions and tends to be 5% to 10% higher than true BMR.

What Is TDEE?

Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns in a full day, combining all sources of energy use. TDEE includes your BMR plus the calories burned through physical activity, the thermic effect of food (TEF), and non-exercise activity thermogenesis (NEAT).

The components of TDEE break down as follows:

BMR (60-75%) — energy for basic life functions at rest
Thermic Effect of Food (8-15%) — energy spent digesting, absorbing, and processing food
Physical Activity (15-30%) — energy spent during intentional exercise
NEAT (variable) — energy spent on non-exercise movements like walking, fidgeting, standing, and household tasks

TDEE is the number that matters most for practical nutrition planning. If you eat fewer calories than your TDEE, you will lose weight over time. If you eat more, you will gain weight. And if you eat at your TDEE, your weight stays roughly the same. This energy balance principle is the foundation of every successful nutrition strategy.

BMR vs TDEE: Key Differences

Feature	BMR	TDEE
Measures	Calories burned at complete rest	Total calories burned per day
Includes activity?	No	Yes
Typical range (adults)	1,200 - 2,000 cal	1,600 - 3,500 cal
Primary use	Baseline metabolic measurement	Calorie target for nutrition planning
Changes daily?	Stays relatively stable	Varies with activity level

How to Calculate BMR

Several scientifically validated equations exist for estimating BMR. Each has different strengths depending on your body composition and the information available to you. The three most widely used formulas are the Mifflin-St Jeor equation, the Harris-Benedict equation, and the Katch-McArdle formula.

Mifflin-St Jeor Equation

Published in 1990, the Mifflin-St Jeor equation is considered the gold standard for BMR estimation in the general population. A 2005 systematic review found it to be the most accurate predictive equation for healthy adults of varying weight categories.

Men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5

Women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) - 161

For example, a 30-year-old male weighing 80 kg (176 lbs) and standing 178 cm (5'10") tall would calculate his BMR as: (10 x 80) + (6.25 x 178) - (5 x 30) + 5 = 800 + 1,112.5 - 150 + 5 = 1,767.5 calories per day.

Harris-Benedict Equation

Originally published in 1919 and revised in 1984 by Roza and Shizgal, the Harris-Benedict equation was the standard for decades before the Mifflin-St Jeor equation gained wider acceptance. It tends to slightly overestimate BMR, particularly in overweight individuals.

Men: BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age)

Women: BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) - (4.330 x age)

Using the same 30-year-old, 80 kg, 178 cm male: 88.362 + (13.397 x 80) + (4.799 x 178) - (5.677 x 30) = 88.362 + 1,071.76 + 854.22 - 170.31 = 1,844 calories per day. Note this result is about 77 calories higher than the Mifflin-St Jeor estimate.

Katch-McArdle Formula

The Katch-McArdle formula is unique because it uses lean body mass (LBM) rather than total weight, height, or sex. This makes it potentially more accurate for individuals who know their body fat percentage, particularly those who are very lean or very muscular.

BMR = 370 + (21.6 x lean body mass in kg)

Lean body mass is calculated as: Total Weight x (1 - Body Fat Percentage as decimal). For the same 80 kg male with 18% body fat: LBM = 80 x (1 - 0.18) = 65.6 kg. BMR = 370 + (21.6 x 65.6) = 370 + 1,417 = 1,787 calories per day.

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How to Calculate TDEE

Once you know your BMR, calculating TDEE is straightforward. Multiply your BMR by an activity factor that reflects your overall daily movement and exercise habits. This activity multiplier system was developed based on research into energy expenditure across different lifestyle patterns.

TDEE = BMR x Activity Multiplier

Activity Level Multipliers

Activity Level	Multiplier	Description	Example
Sedentary	1.2	Little to no exercise, desk job	Office worker who drives to work
Lightly Active	1.375	Light exercise 1-3 days per week	Teacher who walks and exercises twice weekly
Moderately Active	1.55	Moderate exercise 3-5 days per week	Regular gym-goer, 4 days per week
Very Active	1.725	Hard exercise 6-7 days per week	Daily athlete or physical laborer
Extra Active	1.9	Very intense exercise or physical job plus training	Professional athlete in heavy training

Choosing the right activity level is critical because each step up adds 200 to 400 calories to your daily estimate. Most people overestimate their activity level. If you work a desk job and exercise three times per week for 30 to 45 minutes, "lightly active" or the low end of "moderately active" is likely the most accurate selection.

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Practical Examples

Example 1: Sedentary Office Worker

Rachel is a 35-year-old woman who works a desk job, weighs 68 kg (150 lbs), and stands 165 cm (5'5") tall. She does not follow a regular exercise program and drives to work each day.

BMR (Mifflin-St Jeor): (10 x 68) + (6.25 x 165) - (5 x 35) - 161 = 680 + 1,031.25 - 175 - 161 = 1,375 calories
Activity multiplier: 1.2 (sedentary)
TDEE: 1,375 x 1.2 = 1,650 calories per day

If Rachel wants to lose approximately one pound per week, she would aim for roughly 1,150 to 1,200 calories per day, creating a 450-500 calorie deficit. However, since this is close to her BMR, she may benefit more from increasing her activity level rather than restricting calories further. Adding three 30-minute walks per week would raise her TDEE to approximately 1,890 calories (using the 1.375 multiplier), giving her more room for a sustainable calorie deficit.

Example 2: Active Construction Worker

James is a 28-year-old male construction worker who weighs 90 kg (198 lbs) and stands 183 cm (6'0") tall. His job involves heavy lifting and standing for 8 to 10 hours per day, and he also lifts weights three evenings per week.

BMR (Mifflin-St Jeor): (10 x 90) + (6.25 x 183) - (5 x 28) + 5 = 900 + 1,143.75 - 140 + 5 = 1,909 calories
Activity multiplier: 1.725 (very active)
TDEE: 1,909 x 1.725 = 3,293 calories per day

James needs over 3,200 calories per day just to maintain his current weight. If he wants to build muscle while staying lean, he would aim for a modest surplus of 200 to 300 calories above TDEE, targeting roughly 3,500 calories per day with an emphasis on protein intake. Undereating at his activity level could lead to fatigue, muscle loss, and reduced work performance.

Example 3: Moderate Weekend Exerciser

David is a 45-year-old male who works from home, weighs 82 kg (181 lbs), and stands 175 cm (5'9") tall. He jogs for 40 minutes on Saturday and Sunday mornings and takes a 20-minute walk most evenings.

BMR (Mifflin-St Jeor): (10 x 82) + (6.25 x 175) - (5 x 45) + 5 = 820 + 1,093.75 - 225 + 5 = 1,694 calories
Activity multiplier: 1.375 (lightly active)
TDEE: 1,694 x 1.375 = 2,329 calories per day

David might initially assume he is "moderately active" because he exercises on weekends, but since his weekday activity is limited to evening walks, the lightly active multiplier better reflects his overall weekly average. If David used the moderately active multiplier of 1.55, his TDEE estimate would be 2,626 calories, nearly 300 calories higher than reality. Over a month, that miscalculation could mean gaining rather than losing weight.

Factors That Affect Your BMR

Several biological and lifestyle factors influence your metabolic rate. Understanding these helps explain why two people of the same height and weight can have significantly different calorie needs.

Muscle mass. Lean muscle tissue burns approximately 6 calories per pound per day at rest, compared to only 2 calories per pound for fat tissue. People with more muscle mass have higher BMRs, which is why strength training is one of the most effective long-term strategies for raising metabolism.
Age. BMR declines by approximately 1% to 2% per decade after age 20, primarily due to age-related loss of muscle mass. This decline accelerates after age 60, which is why maintaining an active lifestyle and adequate protein intake becomes increasingly important as you age.
Biological sex. Males typically have 5% to 10% higher BMRs than females of the same age and weight, largely because males tend to carry more muscle mass and less body fat. This difference is reflected in the sex-specific constants in the Mifflin-St Jeor and Harris-Benedict equations.
Body size. Larger bodies require more energy to maintain. Taller and heavier individuals burn more calories at rest than smaller individuals, even at the same body fat percentage. This is why the formulas include both weight and height as variables.
Hormones. Thyroid hormones have a significant impact on metabolic rate. Hypothyroidism can reduce BMR by 15% to 40%, while hyperthyroidism can increase it substantially. Other hormones including cortisol, insulin, and testosterone also play roles in metabolic regulation.
Genetics. Research published in the journal Medicine and Science in Sports and Exercise found that genetic factors can account for a 100 to 500 calorie per day variation in BMR between individuals of similar size. You cannot change your genetics, but you can optimize the factors within your control.
Environmental temperature. Extreme heat or cold increases energy expenditure as your body works to regulate its core temperature. Chronic cold exposure can increase BMR modestly by activating brown adipose tissue.

Using TDEE to Reach Your Goals

Once you know your TDEE, you can set a calorie target aligned with your specific goal. The following guidelines provide safe, evidence-based starting points:

Goal	Daily Calorie Target	Expected Rate of Change	Notes
Aggressive fat loss	TDEE - 750 to 1,000	1.5-2 lbs/week	Short-term only; high protein essential
Moderate fat loss	TDEE - 500	~1 lb/week	Most sustainable approach
Gradual fat loss	TDEE - 250	~0.5 lb/week	Best for preserving muscle
Maintenance	TDEE	No change	Maintain current weight
Lean muscle gain	TDEE + 200 to 300	~0.5 lb/week	Minimizes fat gain
Aggressive muscle gain	TDEE + 500	~1 lb/week	Some fat gain expected

These are starting points. Monitor your weight weekly over two to three weeks and adjust by 100 to 200 calories if progress does not match expectations. Weight fluctuates daily due to water retention, sodium intake, and digestion, so focus on the weekly trend rather than daily readings.

Tips for Accurate Metabolic Estimates

Getting an accurate estimate of your metabolic rate sets the stage for success with any nutritional goal. Here are evidence-based strategies to improve the accuracy of your calculations.

Be honest about your activity level. Most people overestimate how active they are. If you exercise three times per week but sit for the remaining waking hours, choose "lightly active" rather than "moderately active." It is always better to underestimate activity and eat slightly more if needed than to overestimate and stall progress.
Use your TDEE as a starting point, not a final answer. No equation is perfectly accurate for every individual. Track your food intake carefully for two to three weeks, weigh yourself under consistent conditions, and adjust your intake based on actual results. If you are maintaining weight, your true TDEE is approximately equal to your average daily intake.
Weigh yourself consistently. Weigh yourself at the same time each morning, after using the bathroom and before eating or drinking. Record daily weights and calculate a weekly average. This eliminates the noise of daily fluctuations and gives you a reliable trend.
Recalculate periodically. As your weight changes, your BMR and TDEE change with it. Recalculate every 10 to 15 pounds of weight change, or every two to three months, to keep your calorie targets accurate.
Account for NEAT variation. Non-exercise activity thermogenesis can vary by 500 to 800 calories per day between individuals. Some people naturally fidget, stand, and move more throughout the day. If you have a desk job, consider standing more, taking walking meetings, or adding short movement breaks to increase your NEAT.

Common Mistakes to Avoid

Using TDEE and BMR interchangeably. Eating at your BMR level when you meant to eat at TDEE creates a calorie deficit you did not intend, potentially leading to fatigue, muscle loss, and metabolic slowdown. Similarly, confusing BMR for TDEE could mean eating 500 to 1,000 fewer calories than you need.
Choosing the wrong activity multiplier. Selecting "very active" when you exercise moderately three times per week can overestimate your TDEE by 300 to 500 calories. Be conservative with your activity level selection and adjust based on real-world results.
Ignoring the thermic effect of food. Different macronutrients require different amounts of energy to digest. Protein has the highest thermic effect (20-30% of its calories are used during digestion), followed by carbohydrates (5-10%) and fats (0-3%). A higher protein diet slightly increases your overall TDEE.
Not recalculating after weight changes. If you lose 20 pounds, your BMR and TDEE drop significantly. Continuing to eat at your original calorie target can cause a plateau. Recalculate after every 10 to 15 pounds of change.
Relying solely on exercise for calorie burn. People often overestimate calories burned during exercise. A 30-minute moderate jog burns roughly 250 to 350 calories, far less than many people assume. Do not eat back all exercise calories unless you are certain of the burn estimate.

Frequently Asked Questions

The Mifflin-St Jeor equation is considered the most accurate BMR formula for the general population. A 2005 systematic review published in the Journal of the American Dietetic Association evaluated multiple predictive equations and concluded that Mifflin-St Jeor predicted resting metabolic rate within 10% of measured values for more individuals than any other equation. If you know your body fat percentage, the Katch-McArdle formula may provide even better accuracy since it factors in lean body mass directly.

Most adults burn between 1,200 and 2,000 calories per day at complete rest, depending on body size, age, sex, and muscle mass. This resting calorie burn, known as your Basal Metabolic Rate, accounts for 60% to 75% of the total calories you burn each day. Larger individuals with more muscle mass tend to have higher BMRs. For example, a 180-pound male in his 30s might burn around 1,800 calories at rest, while a 130-pound female of the same age might burn around 1,350 calories.

Yes, you can increase your BMR primarily by building lean muscle mass through resistance training. Muscle tissue is more metabolically active than fat tissue, burning roughly 6 calories per pound per day compared to about 2 calories per pound for fat. Adding 10 pounds of muscle could increase your daily resting calorie burn by approximately 40 to 50 calories. Other factors that can temporarily raise BMR include consuming adequate protein, getting enough sleep, and staying well-hydrated. However, the most sustainable and impactful strategy is consistently building and maintaining muscle.

BMR decreases with age primarily because of the natural loss of lean muscle mass, a process called sarcopenia that typically begins around age 30 and accelerates after 60. Adults lose an estimated 3% to 8% of muscle mass per decade after 30. Since muscle tissue requires more energy to maintain than fat tissue, less muscle means fewer calories burned at rest. Hormonal changes also play a role, as declining levels of growth hormone, testosterone, and thyroid hormones reduce metabolic activity. Regular strength training and adequate protein intake can significantly slow this age-related decline.

BMR and RMR are closely related but measured under different conditions. Basal Metabolic Rate (BMR) is measured under strict laboratory conditions after 8 hours of sleep, 12 hours of fasting, and in a temperature-neutral environment. Resting Metabolic Rate (RMR) is measured under less restrictive conditions and tends to be 5% to 10% higher than BMR because it includes the small energy cost of recent food digestion and minor physical activity. For practical purposes, most online calculators estimate RMR rather than true BMR, but the terms are often used interchangeably.

TDEE calculators provide a reasonable starting estimate, typically within 10% to 20% of your actual energy expenditure. The main source of error is the activity multiplier, which uses broad categories that may not precisely match your specific activity pattern. Someone who selects moderately active could be off by 200 to 300 calories in either direction depending on their exact exercise intensity, duration, and non-exercise activity. For best results, use a TDEE calculator as a starting point, track your food intake and body weight for two to three weeks, and then adjust based on actual results.

Eating below your BMR is generally not recommended for most people. Your BMR represents the minimum energy your body needs to maintain vital functions like breathing, circulation, and cell repair. Chronically eating below this threshold can trigger metabolic adaptation where your body slows its metabolism to conserve energy, leading to muscle loss, fatigue, hormonal disruption, and nutrient deficiencies. A safer approach is to create a moderate calorie deficit below your TDEE, typically 250 to 750 calories per day, while keeping total intake at or above your BMR. Consult a healthcare provider before starting any very low calorie diet.

Sources & References

Mifflin-St Jeor Original Study (PubMed) — Original 1990 study establishing the Mifflin-St Jeor predictive equation for resting energy expenditure: pubmed.ncbi.nlm.nih.gov
BMR Equation Comparison Study (PubMed) — Systematic review comparing predictive equations for resting metabolic rate in healthy adults: pubmed.ncbi.nlm.nih.gov
CDC Physical Activity Guidelines for Adults — CDC recommendations for adult physical activity levels and health benefits: cdc.gov
Mayo Clinic — Metabolism and Weight Loss — Overview of how metabolism affects weight and strategies for healthy weight management: mayoclinic.org

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Last updated: February 23, 2026