BMR Calculator – Basal Metabolic Rate
Your BMR calculator result represents the minimum number of calories your body needs to maintain basic physiological functions like breathing, circulation, and cell production while at complete rest. This basal metabolic rate accounts for 60-75% of your total daily energy expenditure and serves as the foundation for determining your overall calorie needs. Understanding your BMR is crucial for weight management, as it helps you establish a baseline before adding calories burned through physical activity and daily movement.
The Mifflin-St Jeor equation used in this BMR calculator is generally more accurate than the older Harris-Benedict formula, particularly for overweight individuals and modern populations. Developed in 1990, the Mifflin-St Jeor formula accounts for changes in body composition and lifestyle patterns, typically providing BMR estimates within 10% of measured values. The Harris-Benedict equation, created in 1919, tends to overestimate calorie needs by 5-15% and is less reliable for people with higher body fat percentages.
To find your total daily energy expenditure (TDEE), multiply your BMR by an activity factor: sedentary (1.2), lightly active (1.375), moderately active (1.55), very active (1.725), or extremely active (1.9). Several key factors influence your basal metabolic rate, including age (BMR typically decreases 1-2% per decade after age 30), muscle mass (each pound of muscle burns about 6 calories per day at rest), sex (men generally have 10-15% higher BMRs), and genetics (which can cause 20-30% variation between individuals of similar size and composition).
BMR Formulas Compared
Mifflin-St Jeor (1990) — Recommended:
- Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
- Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Harris-Benedict (revised 1984):
- 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
For example, a 30-year-old man weighing 75 kg and 175 cm tall has a Mifflin-St Jeor BMR of 10(75) + 6.25(175) − 5(30) + 5 = 1,693 kcal/day.
Frequently Asked Questions
What does BMR mean in simple terms?
BMR stands for Basal Metabolic Rate, which is the number of calories your body burns at rest to maintain basic functions like breathing, circulation, and cell production. It represents the minimum energy your body needs to survive if you were lying in bed all day doing nothing.
What is the difference between BMR and TDEE?
BMR is your baseline calorie burn at complete rest, while TDEE (Total Daily Energy Expenditure) includes your BMR plus all calories burned through physical activity, exercise, and digestion. A BMR calculator gives you the starting point, but TDEE provides your total daily calorie needs for weight maintenance.
Which BMR formula is most accurate?
The Mifflin-St Jeor equation is considered the most accurate BMR formula for the general population, with about 90% accuracy. It's more precise than older formulas like Harris-Benedict because it was developed using modern data and accounts for changes in body composition over time.
How can I increase my BMR naturally?
You can boost your BMR by building lean muscle mass through strength training, staying physically active throughout the day, eating enough protein, getting quality sleep, and staying hydrated. Muscle tissue burns more calories at rest than fat tissue, so increasing muscle mass is the most effective way to raise your metabolic rate.
Why does BMR decrease with age?
BMR naturally declines with age primarily due to loss of muscle mass (sarcopenia), hormonal changes, and decreased cellular activity. After age 30, people typically lose 3-8% of muscle mass per decade, and since muscle burns more calories than fat, this directly reduces your baseline metabolic rate as calculated by a BMR calculator.