The Basal Metabolic Rate (BMR) Calculator estimates your basal metabolic rate — the amount of energy expended while at rest in a neutrally temperate environment.
What is Basal Metabolic Rate (BMR)?
Your Basal Metabolic Rate (BMR) is the minimal amount of energy (measured in calories or kilojoules) that your body requires to survive and carry out fundamental vegetative functions while completely at rest. Even when you are sleeping or inactive, your body uses energy to support life-critical processes such as breathing, pumping blood, repairing cells, regulating hormones, and maintaining core temperature.
BMR vs. TDEE
While BMR represents your resting baseline energy requirements, your Total Daily Energy Expenditure (TDEE) accounts for BMR plus any additional energy consumed through daily movement, digestion, and deliberate exercise.
Muscle Mass & Metabolism
Skeletal muscle tissue is highly active metabolically compared to adipose fat tissue. Therefore, individuals with higher lean body mass (higher muscle ratios) exhibit higher resting BMRs even at the same total weight and age.
Standard Global BMR Estimation Formulas
This calculator lets you switch between three globally accepted BMR equations based on your available data:
Widely regarded by fitness and clinical professionals globally as the most reliable standard equation for general populations:
BMR = 10 × Weight (kg) + 6.25 × Height (cm) - 5 × Age (years) + 5BMR = 10 × Weight (kg) + 6.25 × Height (cm) - 5 × Age (years) - 161A revised version (Roza and Shizgal, 1984) of the historic 1918 formula that remains widely used as an alternative clinical baseline:
BMR = 88.362 + 13.397 × Weight (kg) + 4.799 × Height (cm) - 5.677 × Age (years)BMR = 447.593 + 9.247 × Weight (kg) + 3.098 × Height (cm) - 4.330 × Age (years)Ideal for lean individuals or athletes whose body fat percentage is known, as it calculates BMR based on Lean Body Mass (LBM) rather than total weight:
BMR = 370 + 21.6 × LBM (kg)Variables That Impact Your BMR
Your metabolic rate is highly individual and dynamic, influenced by multiple variables:
- Age: BMR generally declines by 1-2% per decade after early adulthood as lean muscle mass naturally diminishes.
- Body Composition: Muscle burns roughly 3 times more resting calories than body fat. Strength training increases resting BMR.
- Hormonal Levels: Thyroid hormones (thyroxine) significantly regulate metabolic speed. Overactive or underactive thyroid levels drastically swing BMR.
- Body Temperature: A fever increases metabolic rate by approximately 7% for every 0.5°C (0.9°F) increase in body temperature.
- Fasting & Calorie Restriction: Long-term low-calorie diets cause the body to downregulate BMR (adaptive thermogenesis) to conserve energy.
How it Works & Formula
W = weight in kg, H = height in cm, A = age in years. Harris-Benedict and Katch-McArdle formulas are also available in settings.
Practical Examples
A 30-year-old male, 5'10", 180 lbs, sedentary lifestyle: BMR ≈ 1,816 cal/day, TDEE ≈ 2,179 cal/day.
A 25-year-old female, 5'5", 130 lbs, exercises 5x/week: BMR ≈ 1,354 cal/day, TDEE ≈ 1,984 cal/day.
Frequently Asked Questions
What is BMR?
BMR (Basal Metabolic Rate) is the number of calories your body needs to accomplish its most basic life-sustaining functions, such as breathing, circulation, cell production, and nutrient processing.
What is the difference between BMR and TDEE?
BMR is the calories burned at rest. TDEE (Total Daily Energy Expenditure) includes BMR plus calories burned through physical activity, the thermic effect of food, and non-exercise activity thermogenesis.
Which BMR formula is the most accurate?
The Mifflin-St Jeor Equation is generally considered the most accurate for most people. The Katch-McArdle formula may be more accurate for lean, athletic individuals since it factors in body fat percentage.
Can BMR be used directly for weight loss planning?
Yes. By knowing your baseline BMR and calculating your TDEE, you can set a safe calorie deficit. Consuming fewer calories than your TDEE (but typically not lower than your baseline BMR without medical supervision) forces your body to draw energy from stored fat.
What is the difference between BMR and Resting Metabolic Rate (RMR)?
BMR requires strict measurement conditions (neutral temp, 12-hour fasting state, immediately upon waking). RMR is measured under less restrictive conditions (sitting quietly, resting but not necessarily fasting), and typically registers about 10% higher than BMR.
How do I increase my BMR?
The most effective way to permanently increase BMR is to build lean muscle mass through resistance training. Muscle tissue requires more energy to maintain at rest. Adequate hydration and protein intake also temporarily increase BMR via the thermic effect of food.