Basal Metabolic Rate Calculator
Calculate basal metabolic rate with our free science calculator. Uses standard scientific formulas with unit conversions and explanations.
Calculator
Adjust values & calculateBMR Comparison (3 Methods)
Suggested Macros (Maintenance)
Formula
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.
Last reviewed: January 2026
Worked Examples
Example 1: Male BMR example
Example 2: Female BMR example
Background & Theory
The Basal Metabolic Rate Calculator applies the following established principles and formulas. Health and medicine calculators are grounded in validated physiological measurement methods established through decades of clinical research. Body Mass Index, or BMI, is calculated by dividing weight in kilograms by height in meters squared (kg/m²), a formula originating from Adolphe Quetelet's 19th-century statistical work and later codified by the WHO into standard classifications: underweight below 18.5, normal weight 18.5 to 24.9, overweight 25 to 29.9, and obese at 30 and above. Basal Metabolic Rate quantifies the minimum energy required to sustain life at rest. The Mifflin-St Jeor equation, published in 1990 and widely regarded as the most accurate for most adults, calculates BMR as (10 × weight in kg) + (6.25 × height in cm) − (5 × age) ± sex adjustment. The older Harris-Benedict equations, revised in 1984 by Roza and Shizgal, remain in common use. Total Daily Energy Expenditure is derived by multiplying BMR by a physical activity factor ranging from 1.2 for sedentary individuals to 1.9 for extremely active ones, following the methodology validated by doubly labeled water studies. Body fat percentage can be estimated without laboratory equipment using the U.S. Navy circumference method, which uses neck, waist, and hip measurements, or via BMI-derived equations adjusted for age and sex. The Jackson-Pollock skinfold method offers higher precision with calipers. Blood pressure classification, according to the American College of Cardiology and the 2017 ACC/AHA guidelines, defines normal as below 120/80 mmHg, elevated as 120 to 129 systolic, and hypertension stage 1 as 130 to 139 systolic or 80 to 89 diastolic. Target heart rate zones for aerobic exercise are derived from maximum heart rate estimates, most commonly using the formula 220 minus age in years, with moderate-intensity training typically defined as 50 to 70 percent of maximum heart rate and vigorous intensity at 70 to 85 percent, consistent with CDC and American Heart Association guidelines. These thresholds guide safe and effective cardiovascular conditioning.
History
The history behind the Basal Metabolic Rate Calculator traces back through the following developments. The history of health measurement stretches back to ancient Greece, where Hippocrates around 400 BCE laid the foundation for observational medicine by systematically recording patient symptoms, diet, and environment. His humoral theory, though scientifically superseded, established the principle that the body operates as an interconnected system subject to measurable imbalance. The transformation toward modern medicine accelerated in the 19th century. Louis Pasteur and Robert Koch developed germ theory in the 1860s and 1870s, identifying microorganisms as disease agents and enabling targeted interventions. Florence Nightingale, working during the Crimean War in the 1850s, introduced statistical analysis to nursing practice, demonstrating through data visualization that sanitation reduced mortality. Her work is foundational to evidence-based health measurement. The discovery of vitamins in the early 20th century, beginning with Casimir Funk's coinage of the term in 1912 and culminating in the isolation of vitamins A through K, created the field of nutritional science and gave rise to dietary reference intake frameworks. The World Health Organization, founded in 1948, subsequently established global standards for health metrics, disease classification through the International Classification of Diseases, and recommended daily allowances. The BMI as a clinical screening tool gained traction in the 1970s through Ancel Keys' large-scale epidemiological work, which validated Quetelet's index as a population-level obesity indicator. Through the 1980s and 1990s, the Framingham Heart Study produced landmark data linking cholesterol, blood pressure, and lifestyle factors to cardiovascular disease risk, directly shaping the numeric thresholds still used in health calculators. The evidence-based medicine movement, formalized by Gordon Guyatt and colleagues at McMaster University in the early 1990s, demanded that all health recommendations derive from systematically graded clinical evidence. The digital health era beginning in the 2000s brought these formulas to consumer devices, wearable sensors, and smartphone applications, expanding access to health self-monitoring on a global scale and enabling population-level data collection that continues to refine clinical reference ranges.
Frequently Asked Questions
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
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).
What inputs do I need to use Basal Metabolic Rate Calculator accurately?
Each field is labelled with the required unit (metric or imperial). Gather your source values before starting — for example, a weight measurement in kilograms, a distance in metres, or a dollar amount — and enter them exactly as measured. The formula section on this page lists every variable and explains what each represents.
How accurate are the results from Basal Metabolic Rate Calculator?
All calculations use established mathematical formulas and are performed with high-precision arithmetic. Results are accurate to the precision shown. For critical decisions in finance, medicine, or engineering, always verify results with a qualified professional.
Can I use the results for professional or academic purposes?
You may use the results for reference and educational purposes. For professional reports, academic papers, or critical decisions, we recommend verifying outputs against peer-reviewed sources or consulting a qualified expert in the relevant field.
References
Reviewed by Rahul Singh, Health & Wellness Specialist · Editorial policy