What Is the Owen Equation?
The Owen Equation is a physiological prediction formula designed to estimate an individual's Resting Energy Expenditure (REE) directly from their total body weight in kilograms, using separate linear regression models for men and women.
Developed in the late 1980s by endocrinologist and metabolic researcher Dr. Oliver E. Owen and colleagues at Temple University School of Medicine, the equations were created after researchers observed that classic equations (such as the 1919 Harris–Benedict formula) tended to overestimate resting caloric expenditure in both lean and obese adults.
Incorporates stature and chronological age adjustments to estimate metabolic rate across broad demographic cohorts.
Applies a high baseline intercept with a conservative weight slope, requiring only your scale weight.
A reappraisal of caloric requirements in healthy men
Owen OE, Holup JL, D'Alessio DA, et al. AJCN 1987; 46(6): 875–885.
PubMed: 3687821 ↗A reappraisal of caloric requirements in healthy women
Owen OE, Kavle E, Owen RS, et al. AJCN 1986; 44(1): 1–19.
PubMed: 3728346 ↗The Owen model applies a fixed baseline intercept plus a linear multiplier for body weight in kilograms, eliminating height and age proxies.
Derived from indirect calorimetry measurements across 60 healthy men (ages 18–82).
Derived from indirect calorimetry measurements across 44 healthy women (ages 18–65).
| Variable / Constant | Mathematical Meaning | Active Applied Value |
|---|---|---|
| REE | Estimated Resting Energy Expenditure (24-hour baseline) | Output in kcal/day |
| Weight | Total body weight in kilograms | 75 kg |
| 879 / 795 | Sex-specific regression y-intercept constant | 879 (Men) |
| 10.2 / 7.18 | Sex-specific weight coefficient (kcal per kg of body mass) | 10.2 kcal/kg |
Why Does the Owen Equation Only Need Weight?
In contrast to multi-variable formulas, Dr. Owen and his research group found that within their measured cohorts of healthy adults, body weight accounted for the vast majority of explained variance in resting metabolic rate.
Adding standing height and age to their statistical models yielded negligible improvements in predictive power ($R^2$) for the general adult sample studied. As a result, Owen formulated parsimonious, weight-only linear equations.
The primary advantage of the Owen equation is extreme ease of use: you only need a bathroom scale and biological sex. The trade-off is that it cannot differentiate between two individuals of identical weight who have significantly different heights, ages, or muscularity levels.
Worked Manual Example: Step-by-Step Calculation
To understand how the mathematics work, consider a male weighing 75.0 kg (165.3 lbs) with a Moderately Active routine (PAL = 1.55):
REE = 879 + (10.2 × Weight in kg)
Weight Component = 10.2 × 75.0 kg = 765.0 kcal/day
REE = 879 + 765.0 = 1,644 kcal/day (6,879 kJ/day)
TDEE = 1,644 kcal REE × 1.55 (Moderately Active) = 2,548 kcal/day (10,661 kJ/day)
REE vs. BMR vs. TDEE: Understanding Physiological Terminology
In commercial fitness apps, the terms REE, BMR, and TDEE are frequently used interchangeably. In metabolic physiology, however, they represent distinct measurement protocols:
| Metric | Full Term | Clinical Testing Protocol | Daily Share |
|---|---|---|---|
| REE (Owen) | Resting Energy Expenditure | Resting quietly in a comfortable, thermo-neutral room ~4 hours post-meal. Typically 3–8% higher than strict BMR. | ~60–75% |
| BMR (Harris–Benedict) | Basal Metabolic Rate | Measured immediately upon waking after a strict 12-hour overnight fast in total thermal neutrality without physical movement. | ~60–70% |
| TDEE | Total Daily Energy Expenditure | Full 24-hour calorie burn: REE + Exercise + Non-Exercise Activity (NEAT) + Thermic Effect of Food (TEF). | 100% |
How Is Resting Energy Expenditure Actually Measured?
It is critical to distinguish between a mathematical prediction and a direct physiological measurement:
Measures real-time gas exchange (oxygen consumption VO₂ and carbon dioxide production VCO₂) via a metabolic cart. Applies the Weir equation to calculate actual cellular oxidation.
Applies population regression constants (like Owen, Mifflin, or Harris–Benedict) to biometric scale values. Serves as a baseline starting estimate for nutritional planning.
Crucial Concept: Same Body Weight ≠ Same Metabolism
Because the Owen equation relies exclusively on body weight and sex, two individuals weighing 75 kg will receive the exact same 1,644 kcal/day prediction. However, if Person A is an athlete with $12%$ body fat and Person B has $28%$ body fat, Person A will have substantially more metabolically active lean muscle tissue, resulting in a higher true resting metabolic rate. For body-composition-sensitive calculations, compare with the Katch–McArdle or Cunningham calculators.
Scientific Limitations of the Owen Equation
Cannot account for differences in body surface area or height among people of identical weight.
Does not model the gradual reduction in organ metabolic flux that occurs across decades of aging.
Treats all body mass uniformly rather than partitioning into fat-free mass and adipose tissue.
Physical activity levels (PAL) are general brackets; actual daily calorie expenditure fluctuates with steps and workouts.
Frequently Asked Questions About the Owen Equation
What is the Owen equation?▼
The Owen equation is a resting energy expenditure (REE) prediction formula developed by Dr. Oliver E. Owen and colleagues (1986/1987) that calculates daily resting calories from body weight and biological sex.
What is the exact Owen formula for men and women?▼
For men: REE = 879 + (10.2 × Weight in kg). For women: REE = 795 + (7.18 × Weight in kg).
Why does the Owen equation only use body weight and sex?▼
In Owen's clinical cohorts, body weight accounted for the majority of metabolic variance. Adding height and age did not statistically improve regression accuracy in their sample, so they published a streamlined weight-based model.
Is Owen an equation for BMR or REE?▼
Owen is formally a Resting Energy Expenditure (REE) formula, measured ~4 hours post-meal under comfortable resting conditions. While many fitness calculators label it BMR, true BMR requires strict 12-hour fasting and waking in a clinical sleep lab.
How is Owen different from Mifflin–St Jeor?▼
Mifflin–St Jeor (1990) incorporates height and age in addition to weight and sex. Owen uses only weight and sex with higher baseline intercepts (879 and 795).
How is Owen different from Harris–Benedict?▼
Harris–Benedict includes age and height multipliers. Owen was developed specifically as a modern re-evaluation because Owen found Harris–Benedict overestimated energy needs in many subjects.
How is Owen different from Schofield?▼
Schofield uses 6 discrete age categories (e.g. 18–29, 30–59, 60+) with different weight multipliers. Owen uses a single linear formula per sex regardless of age.
Is Owen more accurate than Mifflin–St Jeor?▼
In large comparative meta-analyses (such as Frankenfield et al.), Mifflin–St Jeor is generally recognized as the most reliable general-population equation. Owen remains a respected conservative baseline.
Can I use the Owen equation if I know my body fat percentage?▼
The Owen equation does not accept body fat % as an input. If you have verified body composition data from a DEXA scan or calipers, we recommend using the Katch–McArdle or Cunningham calculators.
Is the Owen equation suitable for athletes?▼
Because athletes possess significantly higher muscle mass relative to their scale weight, the Owen equation may underestimate resting metabolic rate in highly muscular individuals.
Can I enter body weight in pounds instead of kilograms?▼
Yes. You can switch to Imperial (lbs). Our calculator converts pounds to kilograms internally using the standard factor 1 lb = 0.45359237 kg before applying the equation.
Why does my Owen result differ from other calculators?▼
Different calculators use different equations (Mifflin, Harris–Benedict, Katch–McArdle). Each equation was regressed on different historical subject cohorts with different input requirements.
How do I calculate TDEE from Owen REE?▼
Multiply your Owen REE by a Physical Activity Level (PAL) multiplier between 1.2 (Sedentary desk job) and 1.9 (Extremely active athlete).
Does each kilogram of weight burn 10.2 calories?▼
No. The 10.2 and 7.18 factors are statistical regression slopes across total body weight, not physiological burn rates of isolated tissue.
Is resting energy expenditure constant throughout the day?▼
Resting energy expenditure fluctuates mildly with circadian rhythm, core body temperature, recent dietary intake (TEF), and sleep cycles.
How should I use this result for weight loss or muscle gain?▼
Use your estimated TDEE as a baseline: subtract 300–500 kcal/day for sustainable fat loss, or add 200–300 kcal/day for lean muscle building. Track your scale weight over 3 weeks to calibrate.
Peer-Reviewed Scientific References
Owen OE, Holup JL, D'Alessio DA, et al. A reappraisal of caloric requirements in healthy men. Am J Clin Nutr, 1987; 46(6): 875–885.
Owen OE, Kavle E, Owen RS, et al. A reappraisal of caloric requirements in healthy women. Am J Clin Nutr, 1986; 44(1): 1–19.
Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults. J Am Diet Assoc, 2005; 105(5): 775–789.
Weir JB. New methods for calculating metabolic rate with special reference to protein metabolism. J Physiol, 1949; 109(1-2): 1–9.
Informational & Personal Awareness Notice:
This calculator provides a mathematical estimate of resting energy expenditure and daily caloric output for nutritional awareness, fitness planning, and journaling purposes. It is not a clinical metabolic test or individualized medical advice. For specialized dietary or metabolic planning, consult an appropriately qualified nutrition professional.