BMR Calculator
Estimate your BMR with Mifflin-St Jeor and Harris-Benedict equations. Enter age, sex, weight, and height to get your daily calorie baseline instantly.
Calculator
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TDEE by Activity Level
Formula
The Mifflin-St Jeor equation calculates BMR based on weight, height, age, and gender. It's the most accurate formula for people of normal weight, overweight, and obese categories. The result represents calories burned at complete rest over 24 hours.
Last reviewed: January 2026
Worked Examples
Example 1: Male BMR Calculation
Example 2: Female BMR with Activity Levels
Background & Theory
The BMR Calculator - Basal Metabolic Rate 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 BMR Calculator - Basal Metabolic Rate 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
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy
BMR Calculator Formula
BMR (Mifflin-St Jeor) = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5 (male) or -161 (female)
The Mifflin-St Jeor equation calculates BMR based on weight, height, age, and gender. It's the most accurate formula for people of normal weight, overweight, and obese categories. The result represents calories burned at complete rest over 24 hours.
BMR Calculator — Worked Examples
Example 1: Male BMR Calculation
Problem: Calculate BMR for a 30-year-old male, 180 lbs (81.6 kg), 5'10\" (177.8 cm) using Mifflin-St Jeor.
Solution: BMR = 10 x 81.6 + 6.25 x 177.8 - 5 x 30 + 5\nBMR = 816 + 1,111.25 - 150 + 5\nBMR = 1,782 calories/day\nHourly burn rate = 1,782 / 24 = 74.3 cal/hour
Result: BMR: 1,782 calories per day (74.3 cal/hour)
Example 2: Female BMR with Activity Levels
Problem: Calculate BMR and TDEE for a 25-year-old female, 135 lbs (61.2 kg), 5'5\" (165.1 cm), moderately active.
Solution: BMR = 10 x 61.2 + 6.25 x 165.1 - 5 x 25 - 161\nBMR = 612 + 1,031.9 - 125 - 161 = 1,358 cal/day\nTDEE = 1,358 x 1.55 = 2,105 cal/day\nWeight loss (500 deficit) = 1,605 cal/day
Result: BMR: 1,358 cal | TDEE: 2,105 cal | Weight loss: 1,605 cal
BMR Calculator — Frequently Asked Questions
What is BMR (Basal Metabolic Rate)?
BMR is the number of calories your body burns at complete rest to maintain vital functions like breathing, blood circulation, cell production, nutrient processing, and temperature regulation. It represents the minimum energy your body needs to survive if you did nothing but lie in bed all day. BMR typically accounts for 60-75% of your total daily calorie expenditure. Factors affecting BMR include age (decreases ~2% per decade after 20), gender (men typically have higher BMR due to more muscle mass), body composition (muscle burns more than fat), and genetics.
What is the difference between BMR and RMR?
BMR (Basal Metabolic Rate) and RMR (Resting Metabolic Rate) are often used interchangeably, but there's a slight technical difference. BMR is measured under very strict conditions - after 8 hours of sleep, 12 hours of fasting, in a dark room at comfortable temperature. RMR is measured under less restrictive conditions and is typically 10-20% higher than BMR because it includes some minimal daily activity. In practice, most calculators and nutritionists use them interchangeably since the difference is small and both serve the same purpose: estimating your baseline calorie needs.
Which BMR formula is most accurate?
The Mifflin-St Jeor equation (1990) is considered the most accurate for most people, as validated by the American Dietetic Association in 2005. It's accurate within 10% for about 82% of people. The revised Harris-Benedict equation (1984) is slightly less accurate but still widely used. The Katch-McArdle formula is most accurate for lean, muscular individuals because it factors in lean body mass rather than total weight. If you know your body fat percentage, Katch-McArdle is preferred. For general use without body composition data, Mifflin-St Jeor is the best choice.
How can I increase my BMR?
The most effective way to increase BMR is building lean muscle mass through resistance training - muscle tissue burns about 6 calories per pound per day at rest, compared to 2 calories for fat. Other strategies include: staying hydrated (dehydration slows metabolism), eating adequate protein (thermic effect of protein is 20-30% of calories consumed), getting enough sleep (sleep deprivation reduces BMR by 5-20%), managing stress (cortisol promotes fat storage), and avoiding very low calorie diets (they trigger metabolic adaptation). High-intensity interval training (HIIT) also temporarily elevates BMR for 24-48 hours post-exercise.
Should I eat below my BMR to lose weight?
No - eating below your BMR for extended periods is not recommended. Your BMR represents the minimum calories needed for basic body functions. Eating below it can cause metabolic adaptation (your body slows its metabolism to conserve energy), muscle loss (your body breaks down muscle for fuel), nutrient deficiencies, hormonal disruption, fatigue, and hair loss. Instead, eat between your BMR and TDEE for weight loss. A safe deficit is 500-750 calories below your TDEE (not BMR), which produces 1-1.5 lbs of fat loss per week while maintaining muscle and metabolic health.
What is BMR and how does it differ from TDEE?
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest just to sustain basic functions — breathing, circulation, cell repair, and temperature regulation. It accounts for 60-75% of total daily energy expenditure. The Mifflin-St Jeor equation (the current clinical standard) calculates BMR as: Men: (10 × kg) + (6.25 × cm) − (5 × age) + 5; Women: (10 × kg) + (6.25 × cm) − (5 × age) − 161. Total Daily Energy Expenditure (TDEE) multiplies BMR by an activity factor: 1.2 (sedentary), 1.375 (lightly active 1-3 days/week), 1.55 (moderately active 3-5 days/week), 1.725 (very active 6-7 days/week), 1.9 (extremely active). TDEE is the calorie level that maintains your current weight.