BMR Calculator
Calculate your Basal Metabolic Rate (calories burned at rest).
Basal Metabolic Rate (BMR) is the number of calories your body requires to perform basic, life-sustaining functions while at complete rest. These functions include breathing, blood circulation, cell production and repair, nutrient processing, protein synthesis, and maintaining body temperature. Essentially, BMR represents the minimum energy your body needs to stay alive.
BMR typically accounts for 60-75% of your total daily energy expenditure (TDEE). The remaining calories are burned through physical activity, the thermic effect of food (calories burned during digestion), and non-exercise activity thermogenesis (NEAT) like fidgeting or maintaining posture.
Understanding your BMR is crucial for weight management. It provides a baseline for calculating your total calorie needs and helps you create appropriate calorie deficits or surpluses for fat loss or muscle gain. However, remember that BMR is just one piece of the puzzle—your actual daily calorie needs depend on your activity level and other factors.
Mifflin-St Jeor Equation (1990)
Currently considered the most accurate formula for the general population, the Mifflin-St Jeor equation has about ±10% accuracy for most people. It's recommended by the Academy of Nutrition and Dietetics.
Men: (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5
Women: (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161
Harris-Benedict Equation (Revised 1984)
The original Harris-Benedict equation from 1918 was revised in 1984 to improve accuracy. While it's a traditional and well-known formula, it's slightly less accurate than Mifflin-St Jeor for modern populations.
Men: 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) - (5.677 × age)
Women: 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) - (4.330 × age)
Katch-McArdle Formula (1996)
Unlike the other formulas, Katch-McArdle is based on lean body mass (total weight minus fat weight) rather than total body weight. This makes it more accurate for lean individuals and athletes, but it requires knowing your body fat percentage.
370 + (21.6 × lean body mass in kg)
Lean body mass = Total weight × (1 - body fat %)
BMR varies significantly between individuals due to multiple factors:
Body Composition
Muscle tissue is metabolically active and burns more calories at rest than fat tissue. People with higher muscle mass have higher BMR. This is why resistance training is valuable for long-term metabolism—more muscle means more calories burned 24/7.
Age
BMR decreases about 2% per decade after age 20, primarily due to loss of muscle mass and hormonal changes. This is why maintaining muscle through strength training becomes increasingly important as we age.
Gender
Men typically have 5-10% higher BMR than women of the same weight, age, and height because men generally have more muscle mass and less body fat. Hormonal differences also play a role.
Genetics
Genetics can influence BMR by 20-30%. Some people naturally have faster or slower metabolisms. However, this difference is typically only 100-300 calories per day, which can be offset through diet and exercise.
Hormones
Thyroid hormones significantly regulate metabolism. Hypothyroidism (underactive thyroid) can lower BMR by 15-40%, while hyperthyroidism can increase it. Other hormones like cortisol, testosterone, and estrogen also affect metabolic rate.
Dieting and Calorie Restriction
Prolonged severe calorie restriction can decrease BMR by 10-20% through metabolic adaptation. This is why very low-calorie diets often lead to weight loss plateaus and why diet breaks can be beneficial during extended fat loss phases.
While related, BMR and TDEE serve different purposes in nutritional planning:
BMR (Basal Metabolic Rate)
Calories burned at complete rest. Represents 60-75% of total daily calories. This is what you'd burn lying in bed all day doing nothing.
TDEE (Total Daily Energy Expenditure)
BMR × Activity Factor. Includes all daily activities: exercise, walking, work, fidgeting, and digestion. This is your actual daily calorie burn.
When to Use Each
- Use BMR: As a starting point, understanding minimum needs, or comparing metabolic health
- Use TDEE: For setting calorie targets for weight loss, maintenance, or gain
For practical nutrition planning, always use TDEE, not BMR. Eating at BMR doesn't account for any activity and will create too large a deficit for most people. Use our TDEE Calculator to find your actual daily calorie needs.
Frequently Asked Questions
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 60-75% of your total daily calorie expenditure and is the minimum energy required to keep your body functioning if you did nothing all day.
The Mifflin-St Jeor equation (1990) is currently considered the most accurate for the general population, recommended by the Academy of Nutrition and Dietetics. It has about ±10% accuracy for most people. The Katch-McArdle formula can be more accurate for lean individuals if you know your body fat percentage, as it's based on lean body mass rather than total weight.
Men typically have higher BMR than women due to having more muscle mass and less body fat. Muscle tissue burns more calories at rest than fat tissue. The formulas account for these physiological differences by using different constants and calculations for each gender.
BMR is calories burned at complete rest, while TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor. TDEE includes all physical activity throughout the day. For example, if your BMR is 1500 calories and you're moderately active (1.55 multiplier), your TDEE would be about 2325 calories.
Several factors influence BMR: Age (decreases about 2% per decade after 20), gender (men typically higher), body composition (more muscle = higher BMR), genetics, hormones (thyroid particularly important), body temperature, and health conditions. Extreme dieting can also lower BMR by 10-20%.
No. Eating only your BMR would not account for any physical activity or digestion. For weight maintenance, eat your TDEE (BMR × activity level). For weight loss, create a moderate deficit from TDEE, not BMR. Eating significantly below BMR long-term can slow metabolism and cause muscle loss.
Build muscle through resistance training (muscle burns more calories than fat), stay active, don't severely restrict calories (can slow metabolism), get adequate sleep, stay hydrated, eat enough protein, and consider HIIT workouts. However, genetics largely determine BMR, so focus on total daily calorie burn (TDEE) instead.
Recalculate every 5-10 pounds of weight change, or every 6-12 months. BMR changes slowly. Age decreases it gradually, but significant weight loss or muscle gain will affect it more noticeably. If you've been dieting for months, your BMR may have adapted downward.
Medical Disclaimer
This BMR calculator provides estimates based on standard equations. Individual metabolic rates can vary due to genetics, health conditions, and other factors. For personalized nutrition advice, consult with a registered dietitian or healthcare provider.