Mifflin-St Jeor TDEE Formula Explained
1. Introduction
Calorie calculation is the foundation of any diet plan. Understanding your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) is critical for setting effective macro and micro nutritional goals for weight loss, maintenance, or muscle gain.
2. What is BMR (Basal Metabolic Rate)
BMR is the amount of energy expended while at rest in a neutrally temperate environment, in the post-absorptive state (meaning that the digestive system is inactive). Physiologically, it represents the calories needed to keep your heart beating, lungs breathing, and brain functioning.
3. The Mifflin-St Jeor Formula
For Men
BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5
For Women
BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161
4. History and Validation
Published in 1990 by Mifflin MD, St Jeor ST et al., in the American Journal of Clinical Nutrition, this formula has been heavily validated. A 2005 systematic review by Frankenfield et al. demonstrated it as the most reliable predictive equation, significantly outperforming the older Harris-Benedict formula.
5. The 5 Activity Multipliers
| Activity Level | Multiplier | Example |
|---|---|---|
| Sedentary | 1.2 | Desk job, little to no exercise |
| Lightly Active | 1.375 | Light exercise 1-3 days/week |
| Moderately Active | 1.55 | Moderate exercise 3-5 days/week |
| Very Active | 1.725 | Heavy exercise 6-7 days/week |
| Extremely Active | 1.9 | Very heavy exercise, physical job |
6. Goal Adjustments
Once you calculate your TDEE, you must adjust it based on your goals. For fat loss, reduce your TDEE by 20%. For lean muscle gain, increase it by 15%. For maintenance, consume your TDEE calories exactly.
7. Clinical Condition Modifiers
Medical conditions affect your BMR. PCOS can reduce metabolic rate by ~5-10%. Hypothyroid patients may need further adjustments pending medication stability. Renal patients must calculate their exact protein targets differently to avoid kidney strain.
8. Limitations
While accurate for the general population, the Mifflin formula may not perfectly apply to extreme athletes with high lean mass, the elderly suffering from sarcopenia, or those with complex metabolic conditions. In such cases, a professional dietitian is recommended.
9. How DietPlanPDF uses this formula
Our intelligent calculator utilizes the Mifflin-St Jeor formula at its core. We automatically apply the appropriate modifiers based on your specific inputs to generate your personalized macros.
10. Get Your Personalized Plan
Calculate your precise TDEE and generate a custom diet plan instantly.
Generate a Free Plan11. References
- Mifflin MD, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990.
- Frankenfield D, et al. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005.
12. Frequently Asked Questions
What is BMR and how does Mifflin-St Jeor calculate it?
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain vital functions. The Mifflin-St Jeor equation calculates it using weight (kg), height (cm), and age: For men: BMR = (10 × weight) + (6.25 × height) − (5 × age) + 5. For women: BMR = (10 × weight) + (6.25 × height) − (5 × age) − 161.
How accurate is the Mifflin-St Jeor equation?
The Mifflin-St Jeor equation predicts resting metabolic rate within 10% of measured values (indirect calorimetry) in approximately 82% of non-obese individuals and 70% of obese individuals, making it the most accurate population-level BMR formula available according to a 2005 systematic review by Frankenfield et al. in the Journal of the American Dietetic Association.
What is TDEE and how is it different from BMR?
TDEE (Total Daily Energy Expenditure) is your actual daily calorie burn accounting for physical activity. It is calculated by multiplying your BMR by an activity factor: Sedentary (1.2), Lightly Active (1.375), Moderately Active (1.55), Very Active (1.725), or Extremely Active (1.9).
How many calories should I eat to lose weight using TDEE?
For fat loss, subtract 20% from your calculated TDEE. For example, if your TDEE is 2,000 kcal/day, your fat loss target is 1,600 kcal/day. This creates a sustainable 400 kcal/day deficit which equates to approximately 0.4 kg of fat loss per week without extreme restriction.