BMR & TDEE Calculator

BMR Calculation Formulas

Mifflin-St Jeor Equation (Used by This Calculator)

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

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

TDEE: BMR × Activity Multiplier

Activity Level Multipliers

Understanding BMR & TDEE

What is Basal Metabolic Rate (BMR)?

Definition: The minimum number of calories your body needs to function at complete rest. This includes breathing, blood circulation, cell production, nutrient processing, and maintaining body temperature. Accounts for 60-75% of total daily calorie burn.

Factors Affecting BMR: Age (decreases 1-2% per decade after 20), gender (men typically 5-10% higher), body composition (muscle burns more than fat), genetics, hormones (thyroid, growth hormone), body size (larger bodies = higher BMR), and temperature (cold increases BMR).

Why It Matters: Understanding BMR helps you determine daily calorie needs for weight loss, maintenance, or gain. Eating significantly below BMR long-term can slow metabolism and cause health issues. BMR is the foundation for all calorie calculations.

What is TDEE (Total Daily Energy Expenditure)?

Definition: The total number of calories you burn in a day, including BMR plus all physical activity. TDEE = BMR × Activity Multiplier. This is the number you should use for planning diet and weight goals.

Components of TDEE: BMR (60-75%), physical activity (15-30%), thermic effect of food (10%, calories burned digesting food), and non-exercise activity thermogenesis or NEAT (fidgeting, standing, daily movements: 100-800 calories).

Using TDEE: Eat at TDEE to maintain weight. Create 500 calorie deficit daily for 1 lb/week loss. Create 500 calorie surplus for 1 lb/week gain. Never eat below BMR consistently. Adjust based on results after 2-4 weeks.

How to Use BMR for Weight Management

Weight Loss: Subtract 500 calories from TDEE for 1 lb/week loss (3,500 calorie deficit per week). Subtract 1,000 calories for 2 lbs/week (maximum recommended). Never eat below 1,200 calories (women) or 1,500 (men) without medical supervision. Combine diet with exercise for best results.

Weight Maintenance: Eat at TDEE level. Monitor weight weekly and adjust ±100-200 calories as needed. Weight fluctuates 2-5 lbs normally due to water, food, hormones. Look for 2-week trends, not daily changes.

Weight Gain: Add 250-500 calories to TDEE for 0.5-1 lb/week gain. Focus on muscle gain with strength training, not just fat gain. Eat protein-rich foods (1g per lb body weight). Progressive overload in workouts essential. Track progress monthly.

Factors That Affect Daily Calorie Burn

Muscle Mass: Muscle burns 6 calories per pound daily at rest vs 2 calories for fat. Someone with 20 lbs more muscle burns ~80 extra calories daily doing nothing. Strength training preserves/builds muscle during weight loss.

Age: Metabolism slows 1-2% per decade after age 20 due to muscle loss and hormonal changes. A 50-year-old burns ~200-300 fewer calories than at 20. Combat this with strength training and staying active.

Gender: Men typically have 5-10% higher BMR due to more muscle mass and testosterone. Average woman: 1,400-1,600 BMR. Average man: 1,600-1,800 BMR. Differences increase with higher activity levels.

Genetics: BMR can vary 20-30% between people of same age, gender, and size. Some people are "fast metabolizers" (burn more easily), others "slow metabolizers" (gain easier). Can't change genetics but can optimize through lifestyle.

Common BMR Myths

Myth: Eating increases metabolism long-term. Reality: Small meal frequency doesn't significantly affect daily burn. Total calories matter most. Thermic effect of food is ~10% regardless of meal timing.

Myth: Cardio is best for metabolism. Reality: Strength training builds muscle, which increases BMR permanently. Cardio burns calories during exercise only. Combine both for optimal results.

Myth: Metabolism is fixed. Reality: Can be increased through muscle building, eating adequate protein, staying active, getting sleep, managing stress, and staying hydrated. Small consistent changes add up.

Myth: Starvation mode stops weight loss. Reality: Extreme restriction does slow metabolism 10-15%, but doesn't stop loss completely. Body adapts but continues losing weight. Very low calories cause muscle loss, which permanently reduces BMR.

Frequently Asked Questions

What is the difference between BMR and TDEE?

BMR is calories burned at complete rest (sleeping 24 hours). TDEE is total daily calories including BMR plus all activity. Example: BMR = 1,500, Activity = Moderate (1.55x), TDEE = 2,325 calories. Use TDEE for diet planning, not BMR. Eating at BMR alone is too low for most people.

How many calories should I eat to lose weight?

Subtract 500 calories from TDEE for 1 lb/week loss (safe, sustainable). Subtract 1,000 for 2 lbs/week (maximum recommended). Never go below 1,200 cal (women) or 1,500 cal (men) without medical supervision. Eating below BMR long-term can slow metabolism and cause health issues. Combine diet with exercise.

Why is my BMR lower than I expected?

Several factors: You may have less muscle mass than average (muscle burns more calories). Previous extreme dieting can lower BMR 5-15% (metabolic adaptation). Age decreases BMR 1-2% per decade. Thyroid or hormonal issues affect metabolism. BMR formulas are estimates ±10%. Track actual results and adjust accordingly.

Does BMR decrease with age?

Yes, BMR decreases approximately 1-2% per decade after age 20, mostly due to muscle loss (sarcopenia) and hormonal changes. A 50-year-old may burn 200-300 fewer calories daily than at 20. Combat this through strength training to maintain muscle, staying active, eating adequate protein, and avoiding crash diets.

Can I increase my BMR?

Yes, through: Building muscle (strength training 2-3x/week), eating adequate protein (1g per lb bodyweight), staying hydrated, getting 7-9 hours sleep, managing stress (cortisol affects metabolism), avoiding very low-calorie diets, eating enough food, and staying active throughout day. Muscle gain most effective long-term strategy.

How accurate are BMR calculations?

Mifflin-St Jeor formula (used here) is accurate within ±10% for most people. Accuracy decreases with obesity, very low/high muscle mass, or metabolic disorders. Gold standard is indirect calorimetry (lab test) or DEXA scan. Use calculated BMR as starting point, track results 2-4 weeks, adjust ±100-200 calories based on progress.

Should I eat my BMR or TDEE?

Eat based on TDEE, not BMR. BMR is too low for active people. For weight loss: TDEE minus 500. Maintenance: TDEE. Weight gain: TDEE plus 250-500. Never consistently eat below BMR - causes muscle loss, slowed metabolism, nutrient deficiencies, fatigue, and hormonal issues. Minimum: 1,200 cal women, 1,500 men.

Why am I not losing weight at calculated deficit?

Common reasons: Underestimating food intake (portion sizes, hidden calories, cooking oils), overestimating exercise burn (fitness trackers overestimate 15-30%), water retention (sodium, hormones, new exercise causes temporary 2-5 lb gain), not enough time (need 2-4 weeks to see trends), or medical issues (thyroid, PCOS, medications). Track accurately, be patient, consult doctor if needed.

Tips for Accurate BMR & TDEE Use

• Be honest about activity: Most people overestimate. If unsure, choose lower level and adjust based on results.
• Track food accurately: Use food scale, measure portions, log everything including oils, sauces, drinks, and bites/tastes.
• Give it time: Weight fluctuates 2-5 lbs daily. Track 2-4 week trends, not daily changes. Take weekly averages.
• Adjust as needed: If no change after 2-3 weeks, reduce calories by 100-200 or increase activity. If losing >2 lbs/week, add 100-200 calories.
• Don't go too low: Minimum 1,200 cal (women), 1,500 (men). Eating too little causes muscle loss, slow metabolism, and binge eating.
• Recalculate regularly: Update BMR after losing/gaining 10+ lbs or changing activity level. TDEE decreases as you lose weight.
• Focus on nutrition: Eat whole foods, adequate protein (0.8-1g per lb), healthy fats, fruits, vegetables. Don't just count calories.
• Combine with exercise: Strength training preserves muscle during weight loss. Cardio adds calorie burn. Both improve results.
• Sleep and stress matter: Poor sleep and high stress increase cortisol, affecting hunger, metabolism, and weight loss.
• Consider professional help: Dietitian can personalize plan. Doctor can check for metabolic issues. Trainer can optimize exercise.

Sample Daily Calorie Goals

Example: 30-Year-Old Woman (5'5", 150 lbs, Moderately Active)

BMR: ~1,450 calories. TDEE: ~2,250 calories (BMR × 1.55). Weight loss: 1,750 cal/day (1 lb/week). Maintenance: 2,250 cal/day. Muscle gain: 2,500 cal/day (0.5 lb/week).

Example: 35-Year-Old Man (5'10", 180 lbs, Lightly Active)

BMR: ~1,750 calories. TDEE: ~2,400 calories (BMR × 1.375). Weight loss: 1,900 cal/day (1 lb/week). Maintenance: 2,400 cal/day. Muscle gain: 2,650 cal/day (0.5 lb/week).

Example: 45-Year-Old Woman (5'3", 160 lbs, Sedentary)

BMR: ~1,350 calories. TDEE: ~1,620 calories (BMR × 1.2). Weight loss: 1,400 cal/day (0.5 lb/week - can't safely do 500 deficit). Maintenance: 1,620 cal/day. Note: Low TDEE; adding activity recommended.

Macronutrient Recommendations

Once you know daily calories, distribute among macros:

• Protein: 0.8-1g per lb bodyweight (more during weight loss or muscle building). 4 calories per gram. Essential for muscle maintenance/growth.
• Fats: 0.3-0.5g per lb bodyweight or 20-35% of calories. 9 calories per gram. Essential for hormones, brain function, vitamin absorption.
• Carbohydrates: Remaining calories. 4 calories per gram. Primary energy source, especially for exercise. Adjust based on activity level.

Example (150 lb person, 2,000 calories): Protein 150g (600 cal), Fat 60g (540 cal), Carbs 215g (860 cal).