Calculate your Basal Metabolic Rate using the Mifflin-St Jeor equation, considered the most accurate BMR formula for the general population. Get TDEE estimates for all activity levels.
The Mifflin-St Jeor equation, developed by MD Mifflin and ST St Jeor in 1990, is widely regarded as the most accurate basal metabolic rate (BMR) formula for the general population. The American Dietetic Association (now the Academy of Nutrition and Dietetics) endorsed this equation in 2005 as the preferred method for estimating resting energy expenditure in healthy individuals. Unlike older equations that tend to overestimate calorie needs, Mifflin-St Jeor was validated on modern populations and consistently produces the closest estimates to actual measured metabolic rates.
BMR represents the number of calories your body burns each day simply to maintain basic life-sustaining functions such as breathing, circulation, cell production, and temperature regulation. Understanding your BMR is the foundation of any evidence-based nutrition plan, whether your goal is weight loss, muscle gain, or maintenance. By multiplying your BMR by an activity factor, you obtain your Total Daily Energy Expenditure (TDEE), which is the total number of calories you actually burn throughout a typical day.
This calculator implements the Mifflin-St Jeor equation with sex-specific formulas, supports both metric and imperial units, and provides TDEE estimates across five standard activity levels. The results give you a science-backed starting point for calorie planning that you can fine-tune based on your individual response.
The Mifflin-St Jeor equation is considered the gold standard for BMR estimation in clinical nutrition and dietetics. Studies consistently show it predicts resting metabolic rate within 10% of measured values for most healthy adults — outperforming the Harris-Benedict, Owen, and WHO/FAO/UNU equations. If you want a single, reliable number to base your calorie targets on, this is the formula most nutrition professionals recommend. It accounts for sex, age, height, and weight without requiring body composition data, making it accessible to everyone.
Male: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + 5 Female: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) − 161 TDEE = BMR × Activity Factor Sedentary: ×1.2 | Lightly Active: ×1.375 | Moderately Active: ×1.55 | Very Active: ×1.725 | Extra Active: ×1.9
Result: 1,743 kcal/day
For a 30-year-old male who is 175 cm tall and weighs 78 kg: BMR = 10 × 78 + 6.25 × 175 − 5 × 30 + 5 = 780 + 1,093.75 − 150 + 5 = 1,728.75 ≈ 1,729 kcal/day. At a moderate activity level (×1.55), his TDEE would be approximately 2,680 kcal/day.
MD Mifflin and ST St Jeor published their equation in the American Journal of Clinical Nutrition in 1990 after studying 498 healthy adults (247 female, 251 male) ranging from 19 to 78 years old. Their goal was to create a more accurate prediction equation for modern populations, since the widely used Harris-Benedict equation was derived from data collected in the early 1900s when average body compositions were quite different from today.
A 2005 evidence analysis by the American Dietetic Association compared five commonly used BMR prediction equations: Harris-Benedict (original and revised), Mifflin-St Jeor, Owen, and WHO/FAO/UNU. The Mifflin-St Jeor equation was found to be the most reliable, predicting RMR within 10% of actual measured values in the highest percentage of both normal-weight and obese subjects. Harris-Benedict tended to overestimate by 5-15% in many individuals, while the Owen equation tended to underestimate.
Once you know your BMR and TDEE, you can design a calorie plan aligned with your goals. For weight maintenance, eat at your TDEE level. For a safe rate of fat loss (0.5-1.0% of body weight per week), create a 500-750 kcal/day deficit. For lean muscle gain, add 250-500 kcal/day above TDEE. Remember that macronutrient distribution (protein, carbohydrate, fat ratios) also matters — starting with 1.6-2.2 g protein per kg of body weight is recommended during calorie restriction to minimize muscle loss.
No prediction equation is perfect. Factors such as genetics, thyroid function, medications, menstrual cycle phase, and recent dieting history can all shift your actual metabolic rate away from predicted values. If you have been dieting for an extended period, your metabolic rate may be lower than predicted due to adaptive thermogenesis. In these cases, a registered dietitian or sports nutritionist who uses indirect calorimetry can provide a directly measured metabolic rate for more precise planning.
The Harris-Benedict equation was originally developed in 1919 on a limited sample and revised in 1984. The Mifflin-St Jeor equation was derived in 1990 from a larger, more diverse, and more contemporary sample. Multiple validation studies, including a comprehensive 2005 review by the American Dietetic Association, found that Mifflin-St Jeor predicted resting metabolic rate within 10% for more individuals than any other non-calorimetry equation.
Basal Metabolic Rate (BMR) is measured under strict laboratory conditions — fasting, lying still, in a thermoneutral environment. Resting Metabolic Rate (RMR) is measured under less strict conditions and is typically 10-20% higher than BMR. The Mifflin-St Jeor equation technically estimates RMR, but the terms are commonly used interchangeably in practical nutrition planning.
For very muscular individuals, the Katch-McArdle or Cunningham equations may be more appropriate because they factor in lean body mass. For individuals with obesity (BMI > 35), all prediction equations lose accuracy, but Mifflin-St Jeor still performs better than most alternatives. In clinical settings for severe obesity, indirect calorimetry is preferred.
A safe caloric deficit for weight loss is typically 500-750 kcal below your TDEE, which corresponds to approximately 0.5-0.7 kg (1-1.5 lb) of weight loss per week. A deficit larger than 1,000 kcal/day is generally not recommended without medical supervision, as it can lead to muscle loss, nutrient deficiencies, and metabolic adaptation.
Recalculate your BMR whenever your weight changes by 5 kg (11 lb) or more, after every birthday (since age is a factor), or every 3-6 months during an active diet or training program. Significant changes in activity level also warrant recalculation of your TDEE multiplier.
No, the original Mifflin-St Jeor equation does not include an ethnicity variable. Some studies suggest it may overestimate BMR in Asian populations and underestimate it in African-American populations by 5-10%. If you fall into these groups, consider the result as a starting estimate and calibrate by tracking actual weight change.
Sedentary (1.2) suits desk workers who rarely exercise. Lightly active (1.375) fits people who walk or do light exercise 1-3 days per week. Moderately active (1.55) applies to those exercising at moderate intensity 3-5 days per week. Very active (1.725) is for hard daily exercise, and extra active (1.9) is for athletes or people with extremely physical jobs. When in doubt, start with a lower factor and adjust upward.
The Mifflin-St Jeor equation was developed and validated primarily for adults aged 19-78. For children and adolescents, the Schofield equation or WHO/FAO/UNU equations are more appropriate, as they were specifically derived from pediatric data sets.