Basal Metabolic Rate Calculator
Calculate basal metabolic rate with our free science calculator. Uses standard scientific formulas with unit conversions and explanations.
Reviewed by Rahul Singh, Health & Wellness Specialist
Formula
Mifflin-St Jeor: BMR = (10 x weight_kg) + (6.25 x height_cm) - (5 x age) + s
Where s = +5 for males and -161 for females. Weight is in kilograms, height in centimeters, age in years. TDEE = BMR x Activity Multiplier (1.2 sedentary to 1.9 very active). The Mifflin-St Jeor equation is recommended by the Academy of Nutrition and Dietetics as the most accurate for healthy adults.
Worked Examples
Example 1: BMR for a 30-Year-Old Male
Problem:Calculate BMR for a 30-year-old male, 175 cm tall, weighing 80 kg, moderately active.
Solution:Mifflin-St Jeor: BMR = (10 x 80) + (6.25 x 175) - (5 x 30) + 5\nBMR = 800 + 1093.75 - 150 + 5 = 1,748.75 kcal/day\nTDEE = 1,749 x 1.55 (moderate activity) = 2,711 kcal/day
Result:BMR = 1,749 kcal/day | TDEE = 2,711 kcal/day
Example 2: BMR for a 25-Year-Old Female
Problem:Calculate BMR for a 25-year-old female, 163 cm tall, weighing 60 kg, lightly active.
Solution:Mifflin-St Jeor: BMR = (10 x 60) + (6.25 x 163) - (5 x 25) - 161\nBMR = 600 + 1018.75 - 125 - 161 = 1,332.75 kcal/day\nTDEE = 1,333 x 1.375 (light activity) = 1,833 kcal/day
Result:BMR = 1,333 kcal/day | TDEE = 1,833 kcal/day
Example 3: Male BMR example
Problem:A 30-year-old male is 175 cm tall, weighs 80 kg, and is moderately active.
Solution:Using Mifflin-St Jeor, the BMR estimate is about 1,749 kcal/day. Multiplying by a moderate activity factor gives a TDEE near 2,711 kcal/day.
Result:BMR: about 1,749 kcal/day | TDEE: about 2,711 kcal/day
Frequently Asked Questions
What is Basal Metabolic Rate (BMR)?
Basal Metabolic Rate is the number of calories your body burns at complete rest to maintain basic life-sustaining functions like breathing, circulation, cell production, and nutrient processing. BMR accounts for about 60-75% of your total daily energy expenditure. It is measured under strict resting conditions: after 12 hours of fasting, 8 hours of sleep, in a temperature-neutral environment. BMR is different from Resting Metabolic Rate (RMR), which is slightly higher because it is measured under less restrictive conditions. Understanding your BMR is the foundation for calculating your total caloric needs.
What is a healthy resting heart rate?
A normal resting heart rate for healthy adults ranges from 60-100 beats per minute (bpm), measured after at least 5 minutes of stillness, ideally first thing in the morning before getting out of bed. Well-trained endurance athletes can have resting rates of 40-60 bpm because their hearts pump a larger volume per beat (higher stroke volume), requiring fewer contractions. A resting HR consistently above 100 bpm (tachycardia) may indicate anemia, hyperthyroidism, dehydration, chronic stress, or cardiovascular strain and warrants medical evaluation. Tracking your resting heart rate over time is a useful fitness marker — a downward trend typically signals improving cardiovascular efficiency as you become more aerobically fit.
How are target heart rate zones calculated?
Target heart rate zones define exercise intensity by expressing effort as a percentage of your heart rate reserve — the range between resting and maximum heart rate. The Karvonen formula: Target HR = ((Max HR − Resting HR) × intensity%) + Resting HR. Max HR is commonly estimated as 220 − age (e.g., 185 bpm for a 35-year-old), though this formula has ±10-12 bpm variability. For a 35-year-old with a resting HR of 65: Zone 2 (aerobic base, 60-70%) = 134-148 bpm; Zone 3 (cardio tempo, 70-80%) = 148-161 bpm; Zone 4 (threshold, 80-90%) = 161-174 bpm. Lower zones burn a higher fat percentage per calorie but fewer calories per minute overall. Higher zones build cardiovascular capacity and post-exercise calorie burn (EPOC).
References
Reviewed by Rahul Singh, Health & Wellness Specialist · Editorial policy