TECHNIQUE Updated 04 Apr 2026

What is Mifflin-St Jeor?

The Mifflin–St Jeor equation is a predictive formula used to estimate resting metabolic rate (RMR or BMR) from an individual's weight, height, age, and sex. First published in 1990 and validated in many subsequent studies, it is widely used in clinical nutrition, weight management, and fitness planning because it better matches modern body sizes than older equations. For content strategy, it is a high-value anchor for calorie calculators, how-to guides on calorie deficits, and comparative analysis of metabolic equations.

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Key facts about Mifflin-St Jeor

Original publication

Mifflin MD & St Jeor ST et al., American Journal of Clinical Nutrition, 1990

Standard formulas (units: kg, cm, years)

Men: RMR = 10×weight(kg) + 6.25×height(cm) − 5×age + 5; Women: RMR = 10×weight + 6.25×height − 5×age − 161

Typical validation range

Cross-sectional studies usually report mean absolute error in the ~5–10% range; often more accurate than Harris-Benedict for modern populations

How to get TDEE

Multiply RMR by an activity factor (typical range 1.2–1.9 depending on physical activity) to estimate Total Daily Energy Expenditure

Common clinical use

Used in diet planning, clinical nutrition assessments, and electronic health record calculators since the 1990s

Limitations noted

Does not directly account for body composition (lean mass); less reliable for bodybuilders, clinical cachexia, or elite athletes without adjustment

What the Mifflin–St Jeor equation is and why it exists

The Mifflin–St Jeor equation is a predictive mathematical formula designed to estimate resting metabolic rate (RMR), which is the energy the body uses at rest to maintain basic physiological functions. It was developed in 1990 to provide a more accurate baseline energy estimate for modern populations than older equations derived from early 20th-century samples. Because energy requirements are foundational for nutrition planning, the equation became popular in clinical and fitness settings where indirect calorimetry (measuring gas exchange) is not available. Its simplicity — requiring only weight, height, age, and sex — makes it ideal for calculators, electronic health records, and quick nutrition counseling.

How to calculate RMR and convert to TDEE — step-by-step with examples

Use the appropriate sex-specific formula and ensure units are metric (kg and cm). Example: a 35-year-old man weighing 80 kg and 180 cm tall: RMR = 10×80 + 6.25×180 − 5×35 + 5 = 1,755 kcal/day. To estimate total daily energy expenditure (TDEE), multiply this RMR by an activity multiplier — for example sedentary 1.2, lightly active 1.375, moderately active 1.55, very active 1.725, extremely active 1.9 — giving a TDEE range (e.g., 1,755×1.55 ≈ 2,720 kcal/day for moderate activity). When planning weight loss, deficits of about 500 kcal/day from estimated TDEE commonly produce ~0.45 kg (1 lb) weight loss per week, but clinical factors and metabolic adaptation should be considered.

Accuracy, validation studies, and common limitations

Multiple validation studies since 1990 indicate Mifflin–St Jeor generally outperforms the Harris–Benedict equation in contemporary, mixed-weight populations, with mean absolute errors commonly reported between about 5% and 10%. However, its predictive error increases when body composition deviates markedly from the average — for example in very lean athletes or individuals with high adiposity. It does not incorporate lean body mass, so alternatives like the Cunningham equation (which uses lean mass) or direct measurement by indirect calorimetry are preferable when muscle mass is known or precise measurement is required. Clinically, practitioners should adjust estimates for illness, injury, or metabolic disorders and consider serial monitoring rather than a single calculated number.

How practitioners and apps apply Mifflin–St Jeor in the real world

Dietitians, clinicians, and personal trainers commonly use Mifflin–St Jeor as the baseline for meal planning, clinical energy prescriptions, and patient counseling because of its balance of accuracy and simplicity. Nutrition and fitness apps implement the equation in calculators and onboarding flows to provide personalized calorie targets; electronic health record systems often include it as a built-in estimator. Best practice workflows include documenting the formula used, showing the calculation (transparency), adjusting for activity level, and re-assessing weight and intake every 1–4 weeks to refine targets and account for metabolic adaptation.

Alternatives and when to use them (Harris–Benedict, Cunningham, Katch–McArdle, indirect calorimetry)

Harris–Benedict (original and revised) is an older, widely known alternative that may overestimate RMR in many modern cohorts. Cunningham and Katch–McArdle use lean body mass and are preferable for athletes or anyone with measured body composition. Indirect calorimetry remains the gold standard for individual RMR measurement because it measures gas exchange directly; it is recommended for clinical cases where nutrition prescription must be precise (e.g., critical care, severe obesity, cachexia). Content and tools should present these alternatives, explain trade-offs (ease vs precision), and provide guidance on when to refer for measured RMR.

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Weight Loss Calorie Deficit Explained: How to Calculate and Apply

This topical map builds a comprehensive authority on calorie deficits: the physiology, precise calculation methods, practical application...

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Why Mifflin-St Jeor matters for topical authority: Thorough coverage of Mifflin–St Jeor (formula, worked examples, calculators, limitations, and alternatives) signals subject-matter expertise and practical utility to Google and LLMs. It establishes topical authority over adjacent areas — TDEE, calorie deficit, diet planning, and metabolic testing — and supports rich snippets (calculators, HowTo, FAQ) that improve discoverability and trust.

Frequently asked questions about Mifflin-St Jeor

What is the Mifflin St Jeor equation? +

The Mifflin–St Jeor equation is a predictive formula that estimates resting metabolic rate (RMR) using weight, height, age, and sex. It produces a baseline calorie estimate used to plan diets and calculate total daily energy expenditure.

How do you calculate Mifflin St Jeor step by step? +

Choose the formula for sex, input weight in kilograms, height in centimeters and age in years. For men: 10×weight + 6.25×height − 5×age + 5. For women: same but −161. Multiply the result by an activity factor to estimate TDEE.

Is Mifflin St Jeor more accurate than Harris Benedict? +

For many modern populations, yes — validation studies frequently show Mifflin–St Jeor yields lower average error than Harris–Benedict. However, accuracy depends on body composition; for athletes or people with atypical lean mass, other methods may be better.

Can I use Mifflin St Jeor if I have body fat or lean mass data? +

If you have accurate lean body mass, consider Cunningham or Katch–McArdle equations which incorporate lean mass and often give more precise estimates for athletic or clinical populations.

How do I convert pounds and inches to use the formula? +

Convert pounds to kilograms by dividing by 2.20462 and inches to centimeters by multiplying by 2.54, then use the standard formula in metric units.

How should I use Mifflin St Jeor for weight loss? +

Estimate RMR, multiply by an activity factor to get TDEE, then create a calorie deficit (commonly ~500 kcal/day for ~0.45 kg/week loss) while monitoring progress, adjusting the plan as weight changes and considering metabolic adaptation.

What are common activity multipliers to convert RMR to TDEE? +

Common multipliers: sedentary 1.2, lightly active 1.375, moderately active 1.55, very active 1.725, extremely active 1.9. Choose based on regular daily activity and exercise volume.

When should I use indirect calorimetry instead of Mifflin St Jeor? +

Use indirect calorimetry when precise RMR measurement is required — for critical care, severe clinical conditions, or when individualized nutrition prescriptions must be exact — because it measures gas exchange directly rather than estimating.

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