Schofield BMR Calculator
WHO-endorsed age-specific metabolic rate calculator for all life stages
Schofield Equation
The Schofield equation is the official World Health Organization (WHO) recommendation for calculating Basal Metabolic Rate (BMR), published in their technical report series. The original 1985 research by Schofield analyzed metabolic data from diverse global populations to create age-specific formulas that provide superior accuracy across all life stages. This comprehensive approach makes it the international standard for nutritional assessment, dietary planning, and clinical applications worldwide.
Age-Specific Precision
Unlike single-formula approaches like Harris-Benedict or Mifflin-St Jeor, the Schofield equation provides six distinct formulas for different age groups (0-3, 3-10, 10-18, 18-30, 30-60, 60+ years). Research validation demonstrates that this age-stratified approach accounts for metabolic changes throughout the lifespan, from rapid infant growth to age-related metabolic decline, resulting in ±5-8% accuracy across all age ranges.
Global Population Validation
The Schofield equations were developed using metabolic data from diverse ethnic and geographic populations, making them more universally applicable than equations derived from single populations. Clinical validation studies confirm their accuracy across different ethnicities, body compositions, and environmental conditions, establishing their role as the preferred choice for international nutrition guidelines and healthcare protocols.
Schofield Equation Formulas by Age Group
Physical Activity Levels & WHO Standards
| Activity Level | Male PAL | Female PAL | Description | Examples |
|---|---|---|---|---|
| Sedentary | 1.3 | 1.3 | Very physically inactive | Desk job, no exercise, minimal walking |
| Lightly Active | 1.6 | 1.5 | Daily routine includes some walking | Light exercise 1-3 days/week, walking |
| Moderate Activity | 1.7 | 1.6 | Regular exercise or active job | Exercise 3-5 days/week, active job |
| Very Active | 2.1 | 1.9 | Intense daily exercise | Hard exercise 6-7 days/week, physical job |
| Extremely Active | 2.4 | 2.2 | Very demanding physical activity | Multiple daily training, manual labor |
Note: Physical Activity Levels (PAL) are based on WHO/FAO recommendations and account for gender differences in metabolic response to activity. These values represent the ratio of total energy expenditure to BMR over a 24-hour period.
Schofield vs. Other BMR Equations
| Equation | Variables Used | Age Range | Accuracy | Best Application |
|---|---|---|---|---|
| Schofield | Age, gender, weight | 0-100+ years (6 age groups) | ±5-8% (all ages) | WHO standard, clinical use, all populations |
| Harris-Benedict | Age, gender, weight, height | Adult populations | ±10-15% (general population) | Historical standard, general use |
| Mifflin-St Jeor | Age, gender, weight, height | Adult populations | ±10-12% (adults) | Overweight/obese individuals |
| Katch-McArdle | Lean body mass | Athletic populations | ±5-8% (athletes) | Athletic individuals with known body fat |
| Cunningham | Lean body mass | Very lean athletes | ±3-5% (elite athletes) | Contest prep, very lean individuals |
Clinical Applications & Professional Use
Medical Nutrition Therapy
Healthcare professionals use Schofield calculations as the foundation for medical nutrition therapy in hospitals, clinics, and rehabilitation centers. Clinical research validates its accuracy for determining caloric needs in patients with diabetes, cardiovascular disease, metabolic disorders, and during recovery from illness or surgery. The age-specific formulas are particularly valuable for pediatric and geriatric patients where metabolic rates differ significantly from healthy young adults.
Population Health & Dietary Guidelines
Government health agencies and international organizations rely on Schofield equations for establishing national dietary guidelines and recommended daily allowances (RDAs). WHO endorsement ensures consistency in nutritional recommendations across countries, supporting public health initiatives, school meal programs, and food assistance programs. The equation’s validation across diverse populations makes it ideal for multicultural societies.
Pediatric & Geriatric Nutrition
The Schofield equation’s age-specific approach makes it the preferred choice for specialized populations. Pediatric nutritionists use the infant, child, and adolescent formulas to support proper growth and development, while geriatricians rely on the 60+ formula to address age-related metabolic changes. The equations account for the higher metabolic rates in growing children and the gradual decline in metabolic rate with aging, ensuring appropriate caloric recommendations throughout the lifespan.
Accuracy & Standard Error of Estimation
| Age Group | Men SEE (kcal/day) | Women SEE (kcal/day) | Accuracy Range | Clinical Significance |
|---|---|---|---|---|
| 0-3 years | 70 | 59 | ±8-12% | Excellent for growth monitoring |
| 3-10 years | 67 | 70 | ±6-10% | Ideal for school nutrition programs |
| 10-18 years | 105 | 111 | ±8-15% | Accounts for adolescent growth spurts |
| 18-30 years | 153 | 119 | ±5-8% | Most accurate for young adults |
| 30-60 years | 167 | 111 | ±5-8% | Excellent for middle-aged populations |
| 60+ years | 164 | 108 | ±6-10% | Superior to single-formula equations |
SEE (Standard Error of Estimation): Represents the typical deviation from actual measured BMR. Lower SEE values indicate higher accuracy. Schofield’s age-specific approach provides consistently lower SEE values compared to single-formula equations across all age groups.
Scientific Research & Validation Studies
Original Schofield Research (1985)
“Predicting basal metabolic rate, new standards and review of previous work”
NCBI PubMed Research –
W.N. Schofield’s landmark 1985 study analyzed metabolic data from thousands of individuals across different
age groups, ethnicities, and geographic regions. This comprehensive analysis established the age-specific
formulas that became the WHO standard, demonstrating superior accuracy compared to existing single-formula approaches.
WHO Technical Report Series
World Health Organization Energy Requirements
WHO Technical Report Series 724 –
The World Health Organization’s official adoption of Schofield equations in their 1985 technical report established
these formulas as the international standard for energy requirement calculations. The report provides comprehensive
validation data and implementation guidelines for healthcare professionals and researchers worldwide.
Optimization Tips & Best Practices
🎯 Maximize Accuracy for Clinical Use
Precise Weight Measurement: Weigh patients at the same time of day, preferably morning after voiding,
in minimal clothing. Use calibrated medical scales and record weight to the nearest 0.1 kg for optimal accuracy.
Age Group Transitions: For individuals near age group boundaries (e.g., 17-19 years, 29-31 years),
consider calculating BMR using both adjacent formulas and taking the average for transitional accuracy.
Medical History Review: Screen for conditions affecting metabolism (thyroid disorders, diabetes, medications)
and consider indirect calorimetry for patients with significant metabolic abnormalities.
📊 Activity Level Assessment
Detailed Activity Logging: Use activity diaries or wearable devices to accurately assess physical activity levels.
Most people overestimate their activity level, leading to overestimated TDEE calculations.
Occupational Considerations: Account for job-related activity separately from recreational exercise.
Manual laborers may need higher PAL factors even with minimal formal exercise.
Seasonal Adjustments: Consider seasonal activity variations and adjust PAL factors accordingly.
Many individuals are more active in summer months and less active during winter.
⚕️ Medical Disclaimer
This Schofield calculator provides estimates based on WHO-established scientific equations and should not replace professional medical advice. Individual metabolic rates can vary significantly due to genetics, medical conditions, medications, and other factors. The Schofield equation provides population averages and may not accurately reflect individual metabolic variations. Consult with healthcare professionals, registered dietitians, or certified nutritionists before making significant dietary changes, especially if you have pre-existing health conditions, are pregnant, breastfeeding, or taking medications that may affect metabolism. The calculations provided are for educational purposes and general guidance only.
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References
- Schofield WN (1985). “Predicting basal metabolic rate, new standards and review of previous work”. Human Nutrition: Clinical Nutrition. 39 Suppl 1: 5–41.
- Tinsley GM, Graybeal AJ, Moore ML. Resting metabolic rate in muscular physique athletes: validity of existing methods and development of new prediction equations. Appl Physiol Nutr Metab. 2019 Apr;44(4):397-406. doi: 10.1139/apnm-2018-0412. Epub 2018 Sep 21. PMID: 30240568.
- Freire R, Pereira GR, Alcantara JMA, Santos R, Hausen M, Itaborahy A. New Predictive Resting Metabolic Rate Equations for High-Level Athletes: A Cross-Validation Study. Med Sci Sports Exerc. 2022 Aug 1;54(8):1335-1345. doi: 10.1249/MSS.0000000000002926. Epub 2022 Apr 1. PMID: 35389940.
- World Health Organisation, Fao, and Unu. Energy and protein requirements. Geneva: WHO, Technical Report Series 724, 1985
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