BMR Calculator
Free BMR Calculator using the Mifflin-St Jeor formula. Calculate your Basal Metabolic Rate, maintenance calories, and daily energy needs. Supports metric and imperial units with charts.
About This Calculator
Basal Metabolic Rate (BMR) is the number of calories your body needs to perform basic life-sustaining functions like breathing, circulation, cell production, and temperature regulation while at complete rest. It represents about 60-75% of your total daily calorie expenditure.
Our BMR calculator uses the Mifflin-St Jeor equation, considered the most accurate formula for estimating BMR in the general population. It also calculates your maintenance calories (TDEE) by applying an activity factor multiplier, helping you understand your total daily energy needs.
The Mifflin-St Jeor Formula:
- For Males: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5
- For Females: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161
Activity Level Multipliers:
- Sedentary (1.2): Little or no exercise
- Light (1.375): Light exercise 1-3 days/week
- Moderate (1.55): Moderate exercise 3-5 days/week
- Active (1.725): Hard exercise 6-7 days/week
- Very Active (1.9): Intense exercise daily or twice/day
Features:
- Mifflin-St Jeor BMR calculation (most accurate formula)
- Maintenance calories based on activity level
- Metric (kg/cm) and imperial (lbs/inches) units
- Visual charts: BMR comparison and energy breakdown
- Detailed breakdown table with all metrics
- Shareable calculation links
Frequently Asked Questions
What is BMR and how is it calculated?
BMR (Basal Metabolic Rate) is the number of calories your body needs to perform basic life-sustaining functions like breathing, circulation, and cell production. Our calculator uses the Mifflin-St Jeor equation: For males: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5. For females: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161. This is considered the most accurate formula for the general population.
What is the difference between BMR and TDEE?
BMR is the calories burned at complete rest, while TDEE (Total Daily Energy Expenditure) includes BMR plus calories burned through physical activity, digestion, and daily movements. TDEE = BMR x activity factor. For example, a person with BMR of 1500 kcal and moderate activity (1.55) has a TDEE of 2325 kcal. Your maintenance calories equal your TDEE.
How accurate is the Mifflin-St Jeor formula?
The Mifflin-St Jeor equation is considered the most accurate BMR formula for the general population, with an accuracy of about 85-90% in healthy individuals. It was developed in 1990 and validated in multiple studies. It replaced the older Harris-Benedict formula which tended to overestimate BMR by 5-15%. However, individual variations in muscle mass, genetics, and medical conditions can affect actual BMR.
What factors affect my BMR?
Several factors influence your BMR: age (BMR decreases 1-2% per decade after age 20), gender (men typically have higher BMR due to more muscle mass), body composition (more muscle increases BMR), genetics (some people naturally have faster metabolisms), hormones (thyroid issues can significantly affect BMR), and body size (larger bodies have higher BMR). Fasting or severe calorie restriction can lower BMR by 10-20%.
How can I increase my BMR naturally?
To naturally increase your BMR: 1) Build muscle through strength training - each pound of muscle burns 6-7 calories daily at rest, 2) Eat enough protein - it requires more energy to digest (thermic effect of food), 3) Stay hydrated - even mild dehydration can slow metabolism, 4) Get adequate sleep - poor sleep lowers BMR by 5-10%, 5) Eat regular meals - severe restriction triggers metabolic slowdown, 6) Green tea and caffeine can provide a small temporary boost.
What is a good BMR for my age and weight?
Average BMR ranges: For adult men: 1600-1800 kcal/day (age 20-40), 1500-1700 (age 40-60), 1300-1500 (60+). For adult women: 1300-1500 kcal/day (age 20-40), 1200-1400 (age 40-60), 1100-1300 (60+). Athletes and very muscular individuals can have BMR 10-20% higher than these averages. Your BMR is individual and depends on your specific body composition and genetics.
What are the activity levels and their multipliers?
Activity level multipliers for TDEE calculation: Sedentary (little or no exercise): 1.2, Light activity (1-3 days/week): 1.375, Moderate activity (3-5 days/week): 1.55, Active (6-7 days/week): 1.725, Very Active (twice/day or intense training): 1.9. Choose the level that best matches your typical weekly activity, not your occasional peak days.
Does BMR differ between men and women?
Yes, men generally have 10-15% higher BMR than women of the same age and weight. This is primarily because men typically have more lean muscle mass and less body fat. Muscle tissue burns more calories at rest than fat tissue. The Mifflin-St Jeor formula accounts for this difference with separate equations for males and females, adding 5 for males and subtracting 161 for females.