BMR & TDEE Calculator
Calculate Your Basal Metabolic Rate & Total Daily Energy Expenditure
BMR & TDEE Calculator
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Activity Level Multipliers
What is BMR (Basal Metabolic Rate)?
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain vital functions like breathing, circulation, cell production, and nutrient processing. It represents the minimum energy required to keep your body alive in a fasted state without any physical activity. BMR accounts for 60-75% of total daily energy expenditure for most people, making it the largest component of calorie burn.
BMR is influenced by multiple factors: body composition (muscle burns more than fat), age (metabolism slows ~2% per decade after 30), gender (men typically have 5-10% higher BMR), genetics, hormones (thyroid function), and body size. A 200-pound muscular man has significantly higher BMR than a 120-pound sedentary woman. Understanding your BMR helps establish baseline calorie needs for weight management goals.
TDEE (Total Daily Energy Expenditure) builds on BMR by multiplying it by an activity factor (1.2-1.9) to account for physical activity, exercise, and non-exercise thermogenesis (fidgeting, standing, daily movements). TDEE represents total calories burned daily, providing the target for maintaining current weight. To lose weight, eat below TDEE; to gain weight, eat above TDEE. The difference between BMR and TDEE can be 400-1500+ calories depending on activity level.
BMR Calculation Formulas
Mifflin-St Jeor Equation (Most Accurate)
This calculator uses the Mifflin-St Jeor equation, validated as the most accurate for modern populations:
For Men:
BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5
For Women:
BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161
Calculating TDEE from BMR
Example - Moderately Active Male:
BMR = 1,800 calories/day
Activity Factor = 1.55 (moderate)
TDEE = 1,800 × 1.55
TDEE = 2,790 calories/day
Alternative: Harris-Benedict Equation
An older but still widely used formula:
Men: BMR = 88.362 + (13.397 × weight kg) + (4.799 × height cm) - (5.677 × age)
Women: BMR = 447.593 + (9.247 × weight kg) + (3.098 × height cm) - (4.330 × age)
Using BMR & TDEE for Weight Goals
Weight Loss (Calorie Deficit)
To lose weight, consume fewer calories than your TDEE. A deficit of 500 calories/day creates approximately 1 pound (0.45 kg) weight loss per week (3500 calories = 1 pound fat). Moderate deficits (250-500 cal/day) are sustainable; aggressive deficits (750-1000 cal/day) accelerate loss but may compromise muscle, energy, and adherence. Never eat below BMR long-term—this can slow metabolism, cause muscle loss, and trigger adaptive thermogenesis.
Weight Maintenance
To maintain current weight, consume calories equal to your TDEE. This balances energy intake with expenditure, keeping weight stable. TDEE isn't fixed—it changes with weight, activity, age, and body composition. Recalculate every 10-15 pounds of weight change or every 6 months. Most people's weight naturally fluctuates 2-5 pounds daily due to water, food volume, and hormones, so track weekly averages, not daily weigh-ins.
Weight Gain (Calorie Surplus)
To gain weight, consume more calories than your TDEE. A surplus of 250-500 calories/day promotes gradual muscle gain when combined with resistance training. Larger surpluses (750-1000 cal/day) accelerate gains but increase fat accumulation. Aim for 0.5-1 pound gain weekly for optimal muscle-to-fat ratio. Without strength training, surplus calories become predominantly fat storage, not muscle growth.
The 3500 Calorie Rule
The traditional "3500 calories = 1 pound of fat" rule provides rough estimates but isn't perfectly accurate. As you lose weight, BMR decreases (smaller body = fewer calories burned), and metabolic adaptation occurs (body becomes more efficient). Similarly, weight gain isn't linear—initial gains include water and glycogen. Use 3500 calories as a guideline, but expect 10-20% variance based on individual metabolic response.
Never Go Below BMR?
The advice "never eat below BMR" is somewhat oversimplified but generally wise. Short-term deficits below BMR (medically supervised Very Low-Calorie Diets at 800-1000 cal/day) can work for rapid weight loss in obesity cases. However, sustained intake below BMR risks muscle loss, metabolic slowdown, nutrient deficiencies, hormonal disruptions, and yo-yo dieting. A safer approach: eat between BMR and TDEE, creating deficits through increased activity rather than extreme restriction.
Factors That Affect BMR
Body Composition (Muscle vs. Fat)
Muscle tissue burns more calories than fat tissue—approximately 6 calories per pound of muscle vs. 2 calories per pound of fat at rest. A person with 160 pounds lean mass has 200-300 cal/day higher BMR than someone with 130 pounds lean mass at the same total weight. This is why strength training is crucial for weight loss—building muscle elevates BMR permanently, making weight maintenance easier long-term.
Age (Metabolic Slowdown)
Metabolism decreases 1-2% per decade after age 30, primarily due to muscle loss (sarcopenia), hormonal changes (declining testosterone/estrogen/growth hormone), and reduced activity. A 50-year-old may have 200-300 cal/day lower BMR than their 20-year-old self at the same weight. However, this decline isn't inevitable—maintaining muscle through resistance training and staying active can preserve BMR despite aging.
Gender Differences
Men typically have 5-10% higher BMR than women due to greater muscle mass, larger body size, and higher testosterone levels. A 6-foot, 200-pound man might have BMR of 2000 calories while a 5'4", 140-pound woman has BMR of 1300 calories. Women also experience BMR fluctuations during menstrual cycles (50-300 cal/day higher during luteal phase) and pregnancy (300-500 cal/day increase).
Genetics & Heredity
Genetic variation accounts for 20-30% of BMR differences between individuals. Some people have naturally "fast" or "slow" metabolisms through FTO gene variants, mitochondrial efficiency, brown adipose tissue activity, and spontaneous physical activity levels (fidgeting, posture changes). However, genetics explains only a few hundred calories daily—lifestyle factors (diet, exercise, sleep) remain more influential for weight management.
Thyroid Function & Hormones
Thyroid hormones (T3/T4) regulate metabolic rate. Hypothyroidism (underactive thyroid) can lower BMR by 200-400 calories/day, causing weight gain and fatigue. Hyperthyroidism (overactive thyroid) increases BMR, causing unintended weight loss. Cortisol, testosterone, estrogen, growth hormone, and insulin also influence metabolism. If BMR seems abnormally low despite normal weight/activity, thyroid testing is recommended.
Metabolic Adaptation (Adaptive Thermogenesis)
During prolonged calorie restriction, the body adapts by lowering BMR beyond what's expected from weight loss alone—sometimes 100-400 calories below predicted levels. This "metabolic slowdown" is a survival mechanism conserving energy. It's why weight loss plateaus occur and why maintaining lost weight is challenging. Strategies to minimize adaptation: moderate deficits (not extreme), diet breaks every 8-12 weeks, adequate protein, and resistance training to preserve muscle.
Tips for Optimizing Your Metabolism
- Build muscle through strength training: Resistance exercise 2-4x weekly increases lean mass, elevating BMR by 50-100+ calories per day permanently.
- Stay active throughout the day: NEAT (Non-Exercise Activity Thermogenesis) from walking, standing, fidgeting can burn 200-500+ extra calories daily.
- Don't crash diet: Avoid extreme deficits below 1200 cal/day (women) or 1500 cal/day (men) to prevent metabolic adaptation.
- Eat enough protein: Protein has higher thermic effect (20-30% of calories burned during digestion) vs. carbs (5-10%) and fat (0-3%).
- Get adequate sleep: Poor sleep (< 7 hours) disrupts hunger hormones, lowers BMR by 5-20%, and increases cortisol.
- Manage stress: Chronic stress elevates cortisol, which promotes fat storage and can lower metabolic rate.
- Stay hydrated: Mild dehydration (1-2%) can temporarily reduce metabolic rate by 2-5%.
- Don't skip meals excessively: While intermittent fasting can work, extreme meal skipping may trigger metabolic slowdown in some people.
- Include HIIT workouts: High-Intensity Interval Training creates "afterburn effect" (EPOC), burning extra calories for 24-48 hours post-workout.
- Recalculate BMR regularly: Update calculations every 10-15 pounds of weight change or every 6 months to maintain accuracy.
Medical Disclaimer
This BMR/TDEE calculator provides estimates based on validated equations but cannot account for individual metabolic variations, medical conditions, or medications affecting metabolism. Calculated values may vary ±10-15% from actual measured BMR. People with thyroid disorders, diabetes, hormonal imbalances, eating disorders, or taking medications affecting metabolism should consult healthcare providers before using these estimates for diet planning. Pregnant and breastfeeding women, children, adolescents, and older adults have unique caloric needs not fully captured by standard formulas. Always work with registered dietitians, physicians, or certified nutritionists for personalized nutrition guidance, especially when creating significant calorie deficits or managing medical conditions. This tool is for educational and planning purposes only, not medical advice.
About the Author
Adam
Co-Founder @ RevisionTown
Math Expert specializing in various curricula including IB, AP, GCSE, IGCSE, and more
If your health and wellness goals include losing, gaining, or maintaining your weight, it’s helpful to learn how to calculate your caloric needs. Knowing how many calories you need can help guide your food and activity choices to reach your goals. This is the whole idea behind the CICO diet, which stands for Calories In Calories Out.
The logic behind the CICO diet is that once you know your caloric needs, you can add, subtract, or meet them to gain, lose, or maintain weight.
Keep reading for a step-by-step guide to calculating your caloric needs using the Mifflin-St Jeor equation. Plus, you’ll learn how to work with that number once you know it.
Step 1: Calculate Your Basal Metabolic Rate (BMR)
It all starts with the basal metabolic rate (BMR). That’s the number of calories your body burns just to stay alive. Even if you stayed in bed all day, your body would still require energy (aka calories) to breathe, pump blood, produce cells and hormones, and so on.
One of the most reliable ways to calculate BMR is by using the Mifflin-St Jeor equation, which factors in your weight, height, age, and gender.
By plugging your own numbers into this formula, you can get a personalized estimate of how many calories your body burns at rest. I say “estimate” because while this is one of the most accurate ways to calculate your BMR, it’s not a perfect science. (More on this later.)
Let’s take an example and calculate this together. For instance, if you’re a 35-year-old woman who’s 5’4’’ and weighs 165 pounds, you’d first need to calculate your height and weight in centimeters and kilograms.
- Height in centimeters = height in inches x 2.54 or 64 x 2.54 = 162.56
- Weight in kilograms = weight in pounds ÷ 2.2 or 165 ÷ 2.2 = 75
Now, let’s plug these numbers into the BMR equation.
- BMR = (10 × 75) + (6.25 × 162.56) – (5 × 35) – 161
- BMR = 750 + 1016 – 175 – 161
- BMR ≈ 1,430 calories/day
This means your body requires about 1,430 calories each day just to maintain essential functions. However, since you don’t spend all day lying down, you need to adjust your energy needs based on how active you are.
Step 2: Adjust BMR Based on Your Activity Level
Now that you know your BMR, you can factor in your activity level to get a more accurate picture of how many calories you really need each day. That’s your total daily energy expenditure (TDEE). TDEE considers your daily movement and adjusts your caloric needs accordingly. (1) To estimate your TDEE, you can use the following activity level multipliers:
Sedentary (little to no exercise)
Use this activity level multiplier if you get minimal activity or movement throughout the day–say, because you drive to work and have a desk job. (1)
Activity multiplier: BMR × 1.2
Lightly active (exercise 1-3 days per week)
This is when you perform some activity–such as going for a walk–up to three days a week. (1)
Activity multiplier: BMR × 1.375
Moderately active (exercise 3-5 days per week)
Let’s say you walk a lot in your day-to-day life and exercise most days; you’d be considered moderately active. (1)
Activity multiplier: BMR × 1.55
Very active (exercise 6-7 days per week)
If you’re engaging in any purposeful exercise–like hopping on the elliptical –most days, or you have a physical job, you’d be considered very active. (1)
Activity multiplier: BMR × 1.725
Super active (hard exercise or physical job)
You’d be considered super active if you pushed yourself hard when you work out–say in spin class–or if you have an intensely physical job. (1)
Activity multiplier: BMR × 1.9
Getting back to our example, if you exercise four times per week, your activity multiplier would be BMR × 1.55. Your BMR was 1,430 calories, so the equation looks like this.(1)
TDEE = 1,430 × 1.55 = 2,216.50 calories/day
This means that for you to maintain your current weight, you’d need around 2,215 calories per day. Now, we’ll adjust this number based on your goals.
Step 3: Set Your Goal: Weight Loss, Maintenance, or Gain
Here’s where you’ll learn how to calculate your caloric needs depending on your personal goal.
For weight loss:
The logic behind the CICO diet is that a pound is roughly equivalent to 3,500 calories. (6) Therefore, to lose weight, you’d subtract 250 to 500 calories from your TDEE.
Using our example TDEE of 2,215, you can cut your intake by 500 calories, aiming for a daily intake of around 1,715 calories. This should lead to a gradual, sustainable weight loss of about 1 pound per week.
Remember that gradual changes are helpful because they don’t feel overwhelming. Also, keep in mind again that while calorie counting is a helpful tool for weight loss, it isn’t a precise science. You may lose more or less weight than predicted after calculating your personal caloric needs for weight loss.
For weight gain:
If you’re trying to gain muscle or increase your weight, you’ll need to consume more calories than your TDEE. Your caloric needs for weight gain can increase by about 500 calories per day, bringing your total to around 2,715 calories.
A calorie counting tool will come in handy as you focus on adding calories for weight gain.
For maintenance:
For weight maintenance, aim to match your calorie intake to your TDEE. In our example, that would mean consuming about 2,215 calories per day.
Whatever your goal, making small, gradual adjustments is the best way to ensure long-term success. Extreme caloric deficits or surpluses can be difficult to sustain and may negatively impact your health. A calorie counting app, like MyFitnessPal, can help you follow the CICO diet for weight gain, loss, or maintenance.