BMR & TDEE Explained — How Many Calories You Burn

Updated July 2026 · Sources: Mifflin-St Jeor (1990), Harris-Benedict (1919), Katch-McArdle, ACE, NIH

What Is BMR?

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain basic physiological functions. It is the energy required to keep your heart beating, lungs breathing, brain functioning, kidneys filtering, body temperature regulated, and cells repairing and dividing. BMR accounts for the largest portion of your total daily calorie burn—typically 60-75% of TDEE for sedentary individuals and 50-60% for very active individuals.

BMR is measured under strict conditions: after 12 hours of fasting, in a thermally neutral environment, while lying awake but completely still. In practice, most people use estimated BMR from formulas rather than laboratory measurement. The most accurate laboratory method is indirect calorimetry—measuring oxygen consumption and carbon dioxide production in a metabolic chamber.

What Is TDEE?

TDEE (Total Daily Energy Expenditure) is your total calorie burn in a 24-hour period. It includes four components:

1. BMR (Basal Metabolic Rate): 60-75% of TDEE. The energy burned at rest for basic life functions.
2. TEF (Thermic Effect of Food): 10-15% of TDEE. The energy required to digest, absorb, and process the food you eat. Protein has the highest TEF (20-30% of its calories), carbohydrates moderate (5-10%), and fat lowest (0-3%).
3. NEAT (Non-Exercise Activity Thermogenesis): 15-20% of TDEE. All the calories burned from daily movement that is not formal exercise: walking, fidgeting, standing, typing, cooking, cleaning, commuting. NEAT varies dramatically between individuals and can differ by 500-1,000+ calories per day.
4. EAT (Exercise Activity Thermogenesis): 0-15% of TDEE. Calories burned during intentional exercise: running, weightlifting, cycling, swimming, sports. For sedentary people, EAT is near zero. For athletes, it can be 15-30% of TDEE.

BMR Formulas Compared

Several formulas estimate BMR from height, weight, age, and gender. The most widely used are:

1. Mifflin-St Jeor Equation (1990) — Recommended

The Mifflin-St Jeor equation is considered the most accurate BMR formula for the general population, particularly for overweight and obese individuals. It was developed by analyzing data from 251 men and 249 women and has been validated in multiple studies.

2. Harris-Benedict Equation (1919) — Historical

The original BMR formula, developed by James Harris and Francis Benedict in 1919 using data from 136 men and 103 women. It overestimates BMR by approximately 5% for modern populations and is less accurate for overweight individuals. Still widely used in older calculators and textbooks.

3. Katch-McArdle Equation — Body Fat-Based

The Katch-McArdle formula uses lean body mass (total weight minus fat mass) rather than total weight. This makes it more accurate for individuals with known body fat percentage, especially athletes with high muscle mass or very lean individuals.

4. Cunningham Equation — Athletes

Developed specifically for athletes and very lean individuals. Similar to Katch-McArdle but with different coefficients. Less commonly used than Mifflin-St Jeor or Katch-McArdle.

Formula Accuracy Comparison

Formula	Accuracy	Best For	Limitations
Mifflin-St Jeor	±5-10%	General population	Less accurate for very lean/very obese
Harris-Benedict	±10-15%	Historical reference	Overestimates by ~5%, outdated data
Katch-McArdle	±5-8%	Athletes, known body fat %	Requires accurate body fat measurement
Cunningham	±5-8%	Very lean athletes	May overestimate for non-athletes

Accuracy measured as mean difference from indirect calorimetry (laboratory gold standard). Mifflin-St Jeor is the most accurate for general populations and is the formula used by our calculator and most modern nutrition tools.

Activity Multipliers: From BMR to TDEE

To calculate TDEE from BMR, multiply BMR by an activity factor that accounts for TEF, NEAT, and EAT combined. The standard multipliers are:

Activity Level	Multiplier	Description	Example Weekly Routine
Sedentary	1.2	Little to no exercise, desk job	No formal exercise, <5,000 steps/day
Lightly Active	1.375	Light exercise 1-3 days/week	1-2 walks + 1 gym session, 5,000-7,000 steps
Moderately Active	1.55	Moderate exercise 3-5 days/week	3 gym sessions + walking, 7,000-10,000 steps
Very Active	1.725	Hard exercise 6-7 days/week	Daily gym + cardio, 10,000-15,000 steps
Extra Active	1.9	Physical job + hard training	Construction worker + 5x gym, 15,000+ steps

These multipliers are estimates. Individual variation in NEAT (fidgeting, walking, standing) can cause TDEE to vary by ±200-500 calories even within the same activity category. Track your actual weight change over 2-4 weeks to fine-tune your TDEE estimate.

Calorie Targets for Weight Goals

Once you know your TDEE, you can set calorie targets for any weight goal:

Weight Loss: Create a Calorie Deficit

A calorie deficit means consuming fewer calories than your TDEE. Your body makes up the difference by burning stored fat (and some muscle, if the deficit is too large or protein is inadequate).

Recommended deficit: 300-500 calories/day for most people. This produces 0.5-1 lb of fat loss per week, which is sustainable and minimizes muscle loss. Larger deficits (750-1,000+ calories) are appropriate for individuals with higher body fat (25%+ for men, 32%+ for women) who have more fat stores to mobilize, but they increase the risk of muscle loss, metabolic slowdown, and adherence failure.

Minimum intake: Do not drop below 1,200 calories/day for women or 1,500 calories/day for men without medical supervision. Very low calorie diets (VLCDs) can cause nutrient deficiencies, muscle loss, gallstones, and metabolic adaptation that makes weight regain more likely.

Weight Maintenance: Eat at TDEE

To maintain your current weight, eat approximately your TDEE. Because TDEE estimates have a ±10-15% margin of error, you may need to adjust based on actual results:

• Track your weight and calorie intake for 2-4 weeks.
• If your weight is stable (±1 lb), your intake equals your true TDEE.
• If you are gaining weight, reduce intake by 100-200 calories/day.
• If you are losing weight, increase intake by 100-200 calories/day.

Muscle Gain: Create a Calorie Surplus

To build muscle, you need a calorie surplus combined with resistance training. The surplus provides the energy and building blocks (amino acids) for muscle protein synthesis.

Larger surpluses (500-1,000+ calories) are not better. Research shows that muscle protein synthesis is maximized at approximately 0.7-1.0g of protein per pound of body weight, and excess calories beyond what is needed for muscle growth are stored as fat. A 500-calorie surplus produces roughly the same muscle gain as a 300-calorie surplus but with significantly more fat gain.

Body Recomposition: Eat at or Near TDEE

Body recomposition—simultaneously losing fat and gaining muscle—is possible for beginners, people returning to training after a layoff, and individuals with higher body fat (20%+ men, 28%+ women). The strategy is to eat at or slightly below TDEE (100-300 calorie deficit) while resistance training with adequate protein (0.7-1.0g/lb).

Recomposition is slower than dedicated bulking or cutting but avoids the fat gain of bulking and the muscle loss risk of aggressive cutting. It is the preferred approach for most people who are not competitive athletes or bodybuilders.

Calorie Target Summary Table

Goal	Calorie Target	Expected Rate	Protein Target	Best For
Aggressive Fat Loss	TDEE - 750-1,000	1.5-2 lbs/week	0.8-1.0g/lb	High body fat, short timeline
Moderate Fat Loss	TDEE - 500	1 lb/week	0.7-1.0g/lb	Most people, sustainable
Slow Fat Loss	TDEE - 250-300	0.5 lb/week	0.7-1.0g/lb	Lean individuals, preserving muscle
Maintenance	TDEE	0 lbs/week	0.6-0.8g/lb	Current weight, performance focus
Lean Muscle Gain	TDEE + 250-300	0.5 lb/week	0.8-1.0g/lb	Minimizing fat gain while building
Moderate Muscle Gain	TDEE + 500	1 lb/week	0.8-1.0g/lb	Beginners, faster bulk

Common Mistakes in Calorie Planning

1. Underestimating intake. Studies show people underestimate their calorie intake by 20-50% when not tracking. Use a food scale and a tracking app (MyFitnessPal, Cronometer, Lose It) for at least 2-4 weeks to establish accurate baseline intake.
2. Overestimating activity level. Most people select "moderately active" when they are actually "lightly active." A 30-minute gym session 3x/week does not make you "moderately active" if you sit at a desk the rest of the time. Be conservative—start with a lower multiplier and adjust based on results.
3. Ignoring NEAT changes. When you cut calories, your body subconsciously reduces NEAT: less fidgeting, slower walking, choosing to sit instead of stand, taking the elevator instead of stairs. This "adaptive thermogenesis" can reduce TDEE by 100-300 calories/day, making deficits less effective than calculated.
4. Chasing the scale. Weight fluctuates 2-5 lbs daily due to water, sodium, carbohydrate intake, digestion, and hormonal cycles. Track a 7-day rolling average rather than daily weight. Judge progress over 2-4 weeks, not 2-4 days.
5. Setting deficits too large. A 1,000+ calorie deficit may produce faster initial weight loss but increases muscle loss, metabolic slowdown, hunger, fatigue, and binge risk. It also makes the diet unsustainable. Most people who lose weight rapidly regain it within 1-3 years.
6. Not adjusting over time. As you lose weight, your BMR decreases (less body mass to maintain). A 500-calorie deficit at 200 lbs becomes a 300-calorie deficit at 170 lbs if you do not adjust. Recalculate TDEE every 10-15 lbs of weight change.
7. Ignoring protein. Protein is the most important macronutrient for body composition. It preserves muscle during deficits, builds muscle during surpluses, increases satiety (reducing hunger), and has the highest thermic effect of food (burns more calories during digestion). Target 0.7-1.0g per pound of body weight (1.6-2.2g/kg).

How to Fine-Tune Your TDEE

Formulas give you a starting point. The only way to know your true TDEE is to track your actual results:

1. Calculate your estimated TDEE using our calculator or the Mifflin-St Jeor formula + activity multiplier.
2. Track everything you eat for 2-4 weeks using a food scale and tracking app. Aim for your estimated TDEE.
3. Weigh yourself daily under consistent conditions (morning, after bathroom, before eating).
4. Calculate your 7-day average weight at the end of each week.
5. Compare week 1 average to week 4 average.
6. If weight is stable (±0.5 lbs over 4 weeks): Your true TDEE ≈ your average intake. Use this as your maintenance calories.
7. If you lost weight: Your true TDEE is higher than your intake. Add 100-200 calories/day to find maintenance.
8. If you gained weight: Your true TDEE is lower than your intake. Subtract 100-200 calories/day to find maintenance.

This process is called "calorie tracking and adjustment" and is the most reliable way to determine your actual energy needs. Most people find their true TDEE is within 10-15% of the formula estimate.