Free Mifflin-St Jeor Calculator
Calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using the Mifflin-St Jeor equation — the most widely recommended formula by nutrition professionals. This free MSJ calculator provides accurate calorie estimates based on your age, weight, height, and activity level.
Your Daily Calorie Needs
0cal
Calculated using Mifflin-St Jeor
BMR
0
calories at rest
BMI
0
Normal
Lean Mass
--
kg estimated
Choose Your Goal
Aggressive
-750 cal
Lose
-500 cal
Maintain
TDEE
Lean Gain
+250 cal
Bulk
+500 cal
Daily Calorie Target
0 calories
Maintenance - no change from TDEE
Recommended Macros (30/40/30 Split)
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What is the Mifflin-St Jeor Equation?
The Mifflin-St Jeor equation was developed in 1990 by Dr. Mark D. Mifflin and Dr. Sachiko T. St Jeor as a more accurate way to estimate Basal Metabolic Rate (BMR) — the number of calories your body burns at complete rest. Published in the American Journal of Clinical Nutrition, the study analyzed 498 healthy individuals and produced a formula that has since become the gold standard for estimating BMR in non-obese adults.
The American Dietetic Association (ADA) officially recommends the Mifflin-St Jeor equation as the most reliable formula for estimating resting metabolic rate. Compared to the older Harris-Benedict equation (1918), the MSJ formula is better calibrated for modern populations and body compositions.
The Mifflin-St Jeor formulas are:
Men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5
Women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161
Activity Factors for the Mifflin-St Jeor Equation
To convert your BMR to Total Daily Energy Expenditure (TDEE), multiply your Mifflin-St Jeor BMR by an activity factor. These activity multipliers account for the additional calories burned through daily movement and exercise beyond your resting metabolism.
| Activity Level | Factor | Description | Example |
|---|---|---|---|
| Sedentary | 1.2 | Little or no exercise, desk job | Office worker who drives to work |
| Lightly Active | 1.375 | Light exercise 1-3 days/week | Walking, light yoga |
| Moderately Active | 1.55 | Moderate exercise 3-5 days/week | Jogging, swimming, cycling |
| Very Active | 1.725 | Hard exercise 6-7 days/week | CrossFit, competitive sports |
| Extremely Active | 1.9 | Very hard exercise, physical job + training | Athletes, construction workers who also train |
Mifflin-St Jeor vs Harris-Benedict: Which Is More Accurate?
The Mifflin-St Jeor equation is widely regarded as the more accurate formula for estimating BMR compared to the Harris-Benedict equation. A 2005 study published in the Journal of the American Dietetic Association reviewed multiple BMR prediction equations and concluded that the Mifflin-St Jeor formula was the most likely to estimate BMR within 10% of measured values. The Harris-Benedict equation, originally developed in 1918 and revised in 1984, tends to overestimate caloric needs by approximately 5%, particularly in overweight and obese individuals.
For most healthy adults who do not know their body fat percentage, the Mifflin-St Jeor formula is the best choice. However, if you know your body fat percentage, the Katch-McArdle formula may provide even more accurate results since it accounts for lean body mass. Athletes and very lean individuals often benefit from using Katch-McArdle, while the general population should rely on the MSJ equation for the most reliable calorie estimates.
Frequently Asked Questions About the Mifflin-St Jeor Calculator
What is the Mifflin-St Jeor equation?
The Mifflin-St Jeor equation is a formula used to estimate your Basal Metabolic Rate (BMR) — the number of calories your body needs at complete rest to maintain basic life-sustaining functions like breathing, circulation, and cell production. Developed in 1990 by Dr. Mark Mifflin and Dr. Sachiko St Jeor, it uses your weight, height, age, and gender to calculate BMR. The American Dietetic Association considers it the most accurate BMR prediction equation for non-obese individuals.
Is the Mifflin-St Jeor formula more accurate than Harris-Benedict?
Yes, research consistently shows that the Mifflin-St Jeor formula is more accurate than the Harris-Benedict equation for most people. A comprehensive review by the American Dietetic Association found that the MSJ formula estimates BMR within 10% of actual measured values more frequently than Harris-Benedict. The older Harris-Benedict equation tends to overestimate calorie needs by about 5%, especially in overweight individuals. For this reason, most nutrition professionals now prefer the Mifflin-St Jeor equation.
What are the activity factors for the Mifflin-St Jeor equation?
After calculating your BMR with the Mifflin-St Jeor formula, you multiply it by an activity factor to get your TDEE: Sedentary (1.2) for desk jobs with little exercise, Lightly Active (1.375) for light exercise 1-3 days per week, Moderately Active (1.55) for moderate exercise 3-5 days per week, Very Active (1.725) for hard exercise 6-7 days per week, and Extremely Active (1.9) for very intense exercise combined with a physical job. Choose the factor that best represents your average weekly activity level.
How do I calculate my BMR using the MSJ formula?
To calculate your BMR using the Mifflin-St Jeor formula, you need your weight in kilograms, height in centimeters, and age in years. For men: BMR = (10 x weight) + (6.25 x height) - (5 x age) + 5. For women: BMR = (10 x weight) + (6.25 x height) - (5 x age) - 161. For example, a 30-year-old male weighing 80 kg and standing 180 cm tall would calculate: (10 x 80) + (6.25 x 180) - (5 x 30) + 5 = 800 + 1,125 - 150 + 5 = 1,780 calories per day at rest.
When was the Mifflin-St Jeor equation developed?
The Mifflin-St Jeor equation was developed and published in 1990 in the American Journal of Clinical Nutrition. The study was conducted by Dr. Mark D. Mifflin, Dr. Sachiko T. St Jeor, and their research colleagues at the University of Nevada. They studied 498 healthy individuals (247 women and 251 men) across a wide range of ages and body weights. In 2005, the American Dietetic Association officially recommended the Mifflin-St Jeor equation as the most accurate for estimating resting metabolic rate in healthy adults.
What is the MSJ calculator used for?
The MSJ (Mifflin-St Jeor) calculator is used to estimate your daily calorie needs by calculating your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE). It is an essential tool for anyone managing their weight — whether losing fat, building muscle, or maintaining. Nutritionists, dietitians, and personal trainers use the MSJ formula to create personalized meal plans and calorie targets for their clients. It is also commonly used in clinical settings to assess metabolic needs for patient care.
Related Tools
Explore our other free nutrition calculators:
- TDEE Calculator - Compare all 3 formulas (Mifflin-St Jeor, Harris-Benedict, Katch-McArdle)
- Katch-McArdle Calculator - Uses body fat percentage for more accurate results
- Macro Calculator - Calculate your optimal protein, carbs, and fat intake
- Body Fat Calculator - Estimate your body fat percentage
For Nutrition Professionals
Are you a dietitian, nutritionist, or personal trainer looking to streamline client BMR and TDEE calculations? Foodzilla uses the Mifflin-St Jeor formula to automatically calculate calorie needs for all your clients and generates personalized meal plans in seconds.
- Built-in Mifflin-St Jeor calculator with multiple formula options
- Automatic macro calculations based on client goals
- AI-powered meal plan generation
- 1,500+ dietitian-approved recipes
- White-label mobile apps for your clients
Disclaimer
This calculator is provided for informational and educational purposes only. The results should not be considered medical advice. Please consult with a qualified healthcare provider, registered dietitian, or physician before making any changes to your diet, exercise routine, or lifestyle. Individual needs may vary based on health conditions, medications, and other factors.
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