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BMR Calculator

Health Updated 2025 100% Private

Calculate your Basal Metabolic Rate (BMR) — the number of calories your body burns at complete rest. Uses the accurate Mifflin-St Jeor equation to help you plan your nutrition and weight management goals.

BMR Calculator

years
kg
cm

What is Basal Metabolic Rate?

Basal Metabolic Rate (BMR) represents the minimum amount of energy your body requires to sustain vital physiological functions while at complete rest. This includes the energy needed for breathing, maintaining body temperature, pumping blood, cell production, and brain function. Remarkably, BMR accounts for approximately 60% to 75% of the total calories you burn each day, making it the largest component of your daily energy expenditure. The remaining calories are burned through physical activity (15-30%) and the thermic effect of food digestion (about 10%).

Understanding your BMR is fundamental to any nutrition or weight management plan. If you know how many calories your body burns at rest, you can calculate your Total Daily Energy Expenditure (TDEE) by factoring in your activity level. This allows you to set precise calorie targets for weight loss, maintenance, or muscle gain. For example, to lose weight at a healthy rate of 0.5 kg per week, you would need to consume approximately 500 calories less than your TDEE each day. Without knowing your BMR, such calculations would be guesswork.

Several factors influence your BMR, some controllable and others not. Body composition is the most significant controllable factor — muscle tissue burns more calories at rest than fat tissue, so increasing muscle mass through strength training raises your BMR. Age causes BMR to naturally decline about 1-2% per decade after age 20, primarily due to muscle loss. Men typically have higher BMRs than women due to greater muscle mass and lower body fat percentage. Genetics also play a role, explaining why some people seem to eat whatever they want without gaining weight while others struggle despite careful eating.

The Mifflin-St Jeor Equation

Our calculator uses the Mifflin-St Jeor equation, considered the most accurate BMR formula for the general population. It was developed in the 1990s and validated against indirect calorimetry measurements.

Mifflin-St Jeor EquationMen: BMR = 10W + 6.25H - 5A + 5
Women: BMR = 10W + 6.25H - 5A - 161

Where W=weight(kg), H=height(cm), A=age(years)
BMR Example

30-year-old male, 70 kg, 170 cm:

  • BMR = (10 × 70) + (6.25 × 170) - (5 × 30) + 5
  • BMR = 700 + 1062.5 - 150 + 5 = 1,617.5 calories/day
  • With moderate activity (1.55x): ~2,507 calories/day

Activity Multipliers Explained

Sedentary (1.2x)
Little or no exercise, desk job. Most modern office workers fall here. Even short walks can bump you to light activity.
Light Activity (1.375x)
Light exercise 1-3 days/week. Includes walking, gentle yoga, or recreational sports. Most people slightly overestimate their activity level.
Moderate (1.55x)
Exercise 3-5 days/week. Includes gym workouts, running, cycling, or physical jobs like nursing or construction.
Very Active (1.725x)
Hard exercise 6-7 days/week. Athletes, military, or physical laborers. Be honest — overestimating leads to weight gain.

BMR Calculator FAQs

What is Basal Metabolic Rate (BMR)?
BMR is the number of calories your body needs to maintain basic physiological functions while at complete rest — including breathing, circulation, cell production, and organ function. It represents about 60-75% of your daily calorie burn. Knowing your BMR is essential for designing effective weight management plans.
Which BMR formula is most accurate?
The Mifflin-St Jeor equation (used in our calculator) is considered the most accurate for most people, validated by the American Dietetic Association. The older Harris-Benedict formula tends to overestimate BMR by about 5%. The Katch-McArdle formula, which uses body fat percentage, may be more accurate for athletes.
Does BMR change with age?
Yes, BMR typically decreases by about 1-2% per decade after age 20. This decline is primarily due to loss of muscle mass (sarcopenia) and hormonal changes. Regular strength training can help preserve muscle mass and maintain a higher BMR as you age.
How can I increase my BMR?
Build muscle through strength training (muscle burns more calories than fat even at rest), eat enough protein (thermic effect of food), stay hydrated, get adequate sleep, avoid crash diets (which lower BMR), and consider high-intensity interval training (HIIT) which can elevate metabolism for hours after exercise.
Is a higher or lower BMR better?
A higher BMR means you burn more calories at rest, making it easier to maintain or lose weight. However, BMR is largely determined by genetics, age, and body composition. Rather than focusing on BMR alone, aim for a healthy body composition and active lifestyle.
Why is my BMR different from my TDEE?
BMR is calories burned at complete rest. TDEE (Total Daily Energy Expenditure) includes BMR plus calories burned through daily activities and exercise. TDEE is always higher than BMR. Use our Calorie Calculator to determine your TDEE based on activity level.