Basal Metabolic Rate (BMR) Calculator — Educational Tool

Estimate your resting caloric expenditure with the Harris-Benedict and Mifflin-St Jeor formulas. Free educational content.

This tool is educational and does not replace professional assessment or official reports. The values presented are estimates based on population-level formulas and may not reflect your individual metabolism.

Educational Results

Harris-Benedict
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kcal/day
Mifflin-St Jeor
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kcal/day
Average BMR
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kcal/day
Estimated TEE
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kcal/day
Activity Level Factor TEE (kcal/day)
Important Notice: The content and the tool on this page are for educational and informational purposes only. They do not replace a consultation, diagnosis, tests, reports, or treatment. Clinical decisions require individualized analysis and assessment by qualified professionals. For any course of action, consult your doctor.

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What is Basal Metabolic Rate (BMR)?

Basal Metabolic Rate (BMR) is the minimum amount of energy — expressed in kilocalories (kcal) — that the body needs to maintain its vital functions at absolute rest: breathing, blood circulation, body temperature maintenance, brain activity, and cell renewal.

In practice, BMR accounts for about 60% to 75% of a person's total daily energy expenditure. This means that even without any physical activity, the body consumes a significant amount of calories just to stay alive.

Formulas used in this calculator

This tool uses two of the most cited formulas in the scientific literature to estimate BMR:

  • Harris-Benedict (revised, 1984): One of the most traditional formulas, originally developed in 1919 and revised by Roza and Shizgal in 1984. It takes into account weight, height, age, and biological sex.
  • Mifflin-St Jeor (1990): Developed more recently, it is considered by several guidelines to be the most accurate for contemporary adult populations.

What is Total Energy Expenditure (TEE)?

TEE is an estimate of the total calories a person expends throughout the day, considering BMR multiplied by a physical activity factor. The factor varies according to the intensity and frequency of exercise.

Important limitations

  • The formulas are based on average population data and may not reflect each person's individual metabolism.
  • Factors such as body composition (ratio of lean mass to fat), health conditions, medication use, and hormonal variations can significantly influence actual metabolism.
  • Accurate energy expenditure assessment requires methods such as indirect calorimetry, available in clinical settings.
  • These values should not be used alone to define diets or meal plans without guidance from a healthcare professional.

Frequently Asked Questions

What is the difference between BMR and TEE?
BMR (Basal Metabolic Rate) measures calorie expenditure at absolute rest — that is, the minimum energy needed for vital functions. TEE (Total Energy Expenditure) includes BMR plus the energy spent on physical activity, digestion, and thermogenesis. TEE is always higher than BMR because it accounts for day-to-day movement.
Which formula is more accurate: Harris-Benedict or Mifflin-St Jeor?
The Mifflin-St Jeor formula (1990) is considered by several guidelines, including the Academy of Nutrition and Dietetics, to be the most accurate for healthy adults. However, both are estimates and may have margins of error between 5% and 15% depending on individual body composition.
Does BMR change with age?
Yes. Generally, BMR tends to decrease with aging, partly due to physiological muscle loss (sarcopenia) and hormonal changes. The formulas include age as a variable for exactly this reason. Regular physical activity can help minimize this reduction.
Can I use BMR to define my diet?
BMR is an educational tool and serves as a starting point for understanding caloric expenditure. However, defining an adequate meal plan requires individualized assessment by a qualified professional, taking into account lab tests, health status, body composition, goals, and food preferences.
Does the calculator work for children or adolescents?
The Harris-Benedict and Mifflin-St Jeor formulas were developed and validated for adult populations. For children and adolescents, there are specific equations (such as Schofield) that take growth and development into account. This calculator is intended for educational use by people over 18.

References

  1. Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr. 1984;40(1):168-182. PubMed
  2. Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. PubMed
  3. 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. PubMed
  4. Academy of Nutrition and Dietetics. Position of the Academy: Interventions for the Treatment of Overweight and Obesity in Adults. J Acad Nutr Diet. 2016. eatright.org
  5. Brazilian Society of Endocrinology and Metabolism (SBEM). Obesity Guidelines. endocrino.org.br

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Important: This content is strictly educational and must not, under any circumstances, be used for self-diagnosis or treatment. It does not replace a consultation with a qualified healthcare professional. Responsibility for the use of the information presented here lies entirely with the user.

I transparently declare that I have no conflict of interest with any pharmaceutical companies that may be mentioned. When I cite brand names or patented products, I do so solely to make the information easier for lay readers to understand and to make medical knowledge more accessible.

All content on this site is intended to inform, educate, and clarify — always free of charge.

I emphasize that no information shared here should be used as the sole criterion for assessment, diagnosis, or therapeutic decisions without proper professional guidance. Each person is unique and must be evaluated individually. Inappropriate use of this information, without professional follow-up, can pose serious health risks.