BMR & TDEE Calculator

This calculator determines your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using the scientifically validated Mifflin-St Jeor equation. Start by selecting your preferred unit system—metric or imperial—using the toggle switch.

Fill in your age, biological sex, current weight, and height. These measurements should be as accurate as possible. Weigh yourself in the morning before eating, and measure your height without shoes. Your biological sex matters because men and women have different muscle mass and metabolic rates on average.

Next, select your activity level. Be honest here—most people overestimate their activity. "Sedentary" means little to no exercise and a desk job. "Lightly active" is light exercise 1-3 days per week. "Moderately active" is moderate exercise 3-5 days per week. "Very active" means hard exercise 6-7 days per week. "Extremely active" is for athletes or people with physically demanding jobs.

Click "Calculate" to see your BMR (calories burned at rest) and TDEE (total daily calorie burn). The calculator also provides calorie targets for weight loss, maintenance, and muscle gain based on your TDEE.

BMR (Basal Metabolic Rate) represents the number of calories your body burns at complete rest just to keep you alive. This includes breathing, circulating blood, controlling body temperature, growing and repairing cells, and all other basic life functions. Your BMR typically accounts for 60-75% of your total daily calorie burn.

TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor. This represents your total calorie burn including all daily activities, exercise, digesting food, and fidgeting. TDEE is the number you should eat to maintain your current weight.

The suggested calorie targets show what to eat for different goals: eat 500 calories below TDEE to lose about 1 pound per week, eat at your TDEE to maintain weight, or eat 500 calories above TDEE to gain about 1 pound per week. These are starting points that may need adjustment based on your individual response.

Remember that these calculations are estimates based on population averages. Your actual metabolism can be 10-15% higher or lower than predicted. Factors like genetics, hormone levels, medications, sleep quality, stress, and previous dieting history all affect your metabolic rate.

Muscle mass is the biggest factor you can control. Muscle tissue burns more calories at rest than fat tissue. This is why strength training is so effective for long-term weight management—it increases your BMR permanently.

Age naturally decreases metabolism. After age 30, most people lose 3-8% of muscle mass per decade if they don't actively strength train. This muscle loss decreases BMR by about 2-3% per decade. The good news is this is preventable through regular resistance training.

Sex plays a role because men typically have more muscle mass and less body fat than women, resulting in higher BMRs. Women's metabolisms also fluctuate throughout the menstrual cycle, with slightly higher calorie burn during the luteal phase.

Body size matters—larger bodies require more energy to maintain. This is why heavier people burn more calories at rest and why calorie needs decrease as you lose weight. You may need to recalculate your TDEE every 10-15 pounds of weight loss.

Genetics, hormones, medications, sleep, stress, and diet history all influence metabolism. Thyroid problems, chronic stress, poor sleep, and repeated crash dieting can all reduce metabolic rate. If you suspect metabolic issues, consult a healthcare provider.

Overestimating activity level: This is the most common error. If you work a desk job and go to the gym 3 times per week for an hour, you're "lightly active," not "very active." Be conservative with your activity estimate—it's better to start lower and adjust up than vice versa.

Not adjusting as weight changes: Your TDEE decreases as you lose weight and increases as you gain weight. Recalculate every 10-15 pounds to ensure your calorie target remains appropriate for your new weight.

Forgetting about food quality: While calories determine weight change, food quality affects hunger, energy, health, and body composition. Don't use your TDEE as permission to eat nothing but junk food as long as calories match.

Being too precise: These calculators provide estimates, not exact numbers. Don't stress over hitting your calorie target to the exact calorie. Focus on weekly averages and how you feel, perform, and progress.

Understanding your TDEE empowers you to take control of your body composition. Instead of guessing or following generic diet plans, you can eat the appropriate amount for your specific goals. This removes the mystery from weight management and gives you a clear roadmap.

Knowing your TDEE helps prevent the common mistake of eating too little during weight loss attempts. Many people drastically undereat, which leads to muscle loss, metabolic slowdown, extreme hunger, and eventual rebound weight gain. With your TDEE, you can create a moderate, sustainable deficit.

Your TDEE also helps you understand why weight loss slows over time. As you lose weight, your TDEE decreases because you have less body mass to maintain. What was once a calorie deficit becomes maintenance. Knowing this helps you avoid frustration and make appropriate adjustments.

Finally, tracking your intake relative to your TDEE teaches you about portion sizes and calorie density. This knowledge is invaluable for long-term weight maintenance—you learn what amounts of different foods keep you at your goal weight, making maintenance natural rather than a constant struggle.